COMPONENTIZED AND EXTENSIBLE WORKFLOW MODEL
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U S provisional patent application No
60/615,543 filed 10/01/2004
TECHNICAL FIELD
[0002] Embodiments of the present invention relate to the field of workflow modeling In particular, embodiments of this invention relate to a componentized and extensible workflow model
BACKGROUND OF THE INVENTION
[0003] Existing systems attempt to map business problems to high-level workflows by modeling the business problem However, real world workflows vary in a variety of dimensions such as (a) execution and modeling complexity, (b) knowledge of the structure of the flow at design time, (c) statically defined or ad-hoc/dynamic, (d) ease of authoring and editing the flow at various points in its lifecycle, and (e) weak or strong association of business logic with the core workflow process Existing models fail to accommodate all these factors
[0004] Further, most existing workflow models are based on either language-based approaches (e g , BPEL4WS, XLANG/S, and WSFL) or application based approaches Language based approaches are high-level workflow languages with a closed set of predefined constructs help model the workflow process to the user/programmer The workflow languages carry all of the semantic information for the closed set of constructs to enable the user to build a workflow model However, the languages are not extensible by the developers and represent a closed set of primitives that constitute the workflow model The languages are tied to the language compiler shipped by the workflow system vendor Only the workflow system product vendor may extend the model by extending the language with a new set of constructs in a future version of the product This often requires upgrading the compiler associated with the language
[0005] Application based approaches are applications which have the workflow capabilities within the application to solve a domain specific problem These applications are not truly extensible nor do they have a programmable model
[0006] With the existing approaches, the issues of complexity, foreknowledge, dynamic workflows, authoring ease, and strength of associations with business logic and core workflows are not adequately addressed There are no extensible, customizable, and re-hostable workflow designer frameworks available to build visual workflow designers to model different classes of workflows Existing systems lack a rapid application development (RAD) style workflow design experience which allows users to graphically design the workflow process and associate the business logic in a programming language of developer's choice In addition, there are no ink-enabled workflow designers [0007] In addition, existing systems fail to provide seamless ad-hoc or dynamic editing for executing workflows Workflow processes are dynamic and mobile in nature and their form cannot be entirely foreseen at design time The workflow processes start in a structured fashion and eventually evolve and change during the course of their execution lifetime There is a need for a workflow authoring framework that allows workflow builders to author various types of workflow models at design time as well as make ad-hoc or dynamic changes to running workflows in a seamless manner Even after a workflow process has been deployed and is running, changes in business requirements often force changing or editing the currently running workflow process There is a need for a system that provides runtime authoring of a workflow process
[0008] In addition, workflow processes deal with cross cutting orthogonal and tangled concerns that span multiple steps of a workflow process model For example, while parts of the workflow process are designed to participate in long running transactions, other parts of the same process are designed for concurrent execution Still other portions of the same workflow process require tracking, while other portions handle business or application level exceptions There is a need to apply certain behaviors to one or more portions of a workflow process
[0009] Some workflow modeling approaches are impractical as they require a complete flow-based description of an entire business process including all exceptions and human interventions Some of these approaches provide additional functionality as exceptions arise, while other approaches exclusively employ a constraint-based approach instead of a flow-based approach to modeling a business process Existing systems implement either the flow-based or constraint-based approach Such systems are too inflexible to model many common business situations
[0010] Accordingly, a componentized and extensible workflow model is desired to address one or more of these and other disadvantages
SUMMARY OF THE INVENTION
[0011] Embodiments of the invention provide an extensible framework for building a componentized workflow model In particular, each step of a workflow process has an associated component model that describes design time aspects, compile time aspects, and runtime aspects of the workflow step Further, any developer may extend the core workflow model by authoring these components The invention includes a workflow engine that is flexible and powerful enough to coordinate the execution of various kinds of workflows including highly formal machine-to-machine processes, constraint-based ad-hoc human workflows, and workflows having a mixture of flow-based and constraint-based approaches The workflow engine permits activation, execution, query, and control capabilities against executing workflows For example, the invention permits ad-hoc and dynamic changes to executing workflows The workflow engine is rehostable or embeddable in a variety of host environments including both server and client environments Each specific host environment marries the workflow engine to a set of service providers The aggregate capabilities of the service providers determine the kinds of workflows that may be executed in the specific host environment [0012] Other embodiments of the invention provide a declarative format such as an extensible orchestration markup language (XOML) for serializing a workflow model The declarative format enables a user to extend the workflow model by writing a set of components The semantics corresponding to the various steps of a workflow process are encapsulated in an activity validator component which validates and enforces the semantics for a given component at compile time Embodiments of the declarative format of the invention further enable the declaration and association of data with various elements of the workflow model The declarative format supports the transformation of the data through the workflow For example, the format represents external data sources such as databases or files, code snippets, and business rules within the workflow model declaratively [0013] An embodiment of the invention provides an extensible, customizable, and rehostable workflow designer framework to build graphical/visual workflow designers to model different classes of workflows Another embodiment of the invention supports a rapid application development style workflow design experience to allow users to graphically design a workflow process and associate business logic in any programming language Embodiments of the invention also provide ink support using pen and tablet technologies The invention provides a free form drawing surface in which a workflow
drawn by a user is converted into an internal representation The invention supports creation and modification of the workflows via ink editing on the existing drawing surface (e g , add/delete activities), and ink annotation of existing workflows (e g , comments, suggestions, or reminders hand-drawn on the design surface)
[0014] Still other embodiments of the invention provide components for capturing cross cutting behaviors in a declarative way and applying the behaviors to selected portions of a workflow model Other embodiments of the invention execute the selected portions of the workflow model in the context of the behaviors associated therewith Embodiments of the invention provide a framework, reusable components, and a language to deal with cross cutting orthogonal and tangled concerns that span multiple steps of a workflow process model
[0015] In accordance with one aspect of the invention, a computer-implemented method models a workflow The workflow includes activities and the workflow models a business process The method includes presenting a plurality of activities, receiving a selection of the presented activities by a user, and serializing the received activities to create a persistent representation of the workflow
[0016] In accordance with another aspect of the invention, one or more computer-readable media have computer-executable components for modeling a workflow The workflow includes activities and the workflow models a business process The components include a palette component for presenting a plurality of activities The components also include an interface component for receiving, from a user, a selection and hierarchical organization of the activities presented by the palette component The components also include a declarative component for serializing the activities received by the interface component to create a persistent representation of the workflow
[0017] In accordance with yet another aspect of the invention, a computer-implemented system models a workflow The workflow includes activities and the workflow models a business process The computer-implemented system includes a package identifying a plurality of activities The system also includes an interface for selecting and interrelating one or more of the activities from the package to create a workflow The system also includes a senahzer for serializing the received activities to create a persistent representation of the workflow
[0018] Alternatively, the invention may comprise various other methods and apparatuses [0019] Other features will be m part apparent and m part pointed out hereinafter
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG 1 is an exemplary workflow containing tasks and control flow composite
activities
[0021] FIG 2 illustrates an exemplary activity inheritance tree
[0022] FIG 3 illustrates an exemplary component model
[0023] FIG 4 illustrates an exemplary component model lifecycle
[0024] FIG 5 is a high-level application user interface for authoring workflows that
relies upon wizards for specification of the workflow
[0025] FIG 6 illustrates an exemplary workflow designer
[0026] FIG 7 illustrates an orchestration program including a receive activity followed
by a send activity
[0027] FIG 8 illustrates the serialization of objects in a graph
[0028] FIG 9 illustrates a schedule definition and the relationship between a visual
workflow, a serialized representation in XOML of the workflow, and the code beside of the
workflow
[0029] FIG 10 is a block diagram illustrating one example of a suitable computing
system environment in which the invention may be implemented
[0030] Appendix A describes exemplary activities
[0031] Appendix B describes exemplary activity designer interfaces
[0032] Appendix C describes activity validation
[0033] Appendix D describes exemplary application programming interfaces of the
invention
[0034] Corresponding reference characters indicate corresponding parts throughout the
drawings
DETAILED DESCRIPTION OF THE INVENTION
[0035] Embodiments of the invention model a workflow representing a process such as a business process Business processes are dependant and ordered tasks, activities, or the like that result in predictable and repeatable outcomes Including an organization's operating procedures, institutional working knowledge, and information resources, business processes are designed to satisfy defined business objectives in an efficient and timely manner In an efficient environment, the functional components of a process can be readily identified, adapted, and deployed to address ever-changing corporate requirements The workflow is an end user's experience interacting with the tasks in a business process Tasks are modeled as activities, components, or the like, each representing a unit of work that is performed by a person or machine In one embodiment, a plurality of activities is presented to a user The user selects and organizes the activities to create the workflow The created workflow is executed to model the business process Referring first to FIG 1, an exemplary workflow 100 contains tasks and control flow composite activities
[0036] In one example, an orchestration engine workflow model supports modeling, authoring and executing different classes of workflows Examples include modeling a given problem in terms of a structured set of steps that occur in an ordered sequence or as a set of asynchronous events The orchestration engine coordinates the execution of schedules A schedule is an organized set of activities that is arranged hierarchically in a tree structure The execution context of, and the shared data visible to, an executing activity is provided by a scope Each activity represents a component that encapsulates metadata for the step in a workflow process The activity is the basic unit of execution in the workflow model and has associated properties, handlers, constraints and events Each activity may be configured by user code in any programming language For example, the user code may represent business or application logic or rules written in common language runtime (CLR) languages Each activity supports pre-interception hooks and post-interception hooks into execution in the user code Each activity has associated runtime execution semantics and behavior (e g , state management, transactions, event handling and exception handling) Activities may share state with other activities Activities may be primitive activities or grouped into a composite activity A primitive or basic activity has no substructure (e g , child activities), and thus is a leaf node in a tree structure A composite activity contains substructure (e g , it is the parent of one or more child activities) [0038] In one embodiment, activities are of three types simple activity, container activity and root activity In this embodiment, there is one root activity in the model, and
none or any quantity of simple activities or container activities inside the root activity A container activity may include simple or container activities The entire workflow process may be used as an activity to build higher-order workflow processes Further, an activity may be interruptible or non-interruptible A non-mterruptible composite activity does not include interruptible activities A non-interruptible activity lacks services that would cause the activity to block
[0039] The orchestration engine provides an exemplary set of activities Referring to FIG 2, an activity inheritance tree illustrates exemplary activities The exemplary activities listed in FIG 2 are described in detail in Appendix A In addition, any user may write one or more activities to extend the workflow model For example, the user may write activities for a specific business problem, domain, workflow standard (e g business process execution language), or a target platform The orchestration engine may provide a rich set of services to the user for writing activities which include, for example, services of analyzing code, type resolution and type system, services for serialization, and rendering [0040] In one embodiment, each activity has at least three parts metadata, instance data, and execution logic The metadata of the activity defines data properties that may be configured For example, some activities may share a common set of metadata defined in an activity abstract base class Each activity declares its own additional metadata properties according to its needs by extending this class
[0041] The values of metadata properties will be shared by all instances of that activity across the instances of the schedule where the activity was configured For example, if a user creates a schedule A and adds a send activity to it, the send activity is given identification information (e g , "001") as part of its metadata A second send activity added to the schedule would receive its own unique identification information (e g , "002") Once multiple instances of schedule A are created and executed, all instances of send "001" will share metadata values In contrast, the instance data of an activity defines a set of data which is specific to the instance of the activity in a running schedule instance For example, a delay activity may offer a read-only property on its instance data that is the date and time value representing the delay activity's timeout value This value is available once the delay activity has begun executing, and it is most likely different for every single instance of the delay activity It is common to refer to instances of schedules, and especially instances of activities and tasks, without qualifying the reference with "instance " [0042] Composite activities have their set of child activities as another element Child activities are considered metadata in one embodiment The orchestration engine model
explicitly permits manipulation of this metadata at runtime within an instance of the schedule It is possible to add new child activities to a composite activity that is part of an executing schedule instance such that only the metadata (activity tree) for that schedule instance is affected
[0043] Referring next to FIG 3, each activity has an associated set of components that forms the component model for the activity The associated set of components includes an activity executor, an activity designer, an activity senahzer, an activity validator (e g , semantic checker), and an activity code generator The activity executor is a stateless component that implements the execution semantics for the activity The activity executor works with the metadata of an activity to implement the activity A core scheduler acts as a service provider for the activity executor to provide services to the activity executor [0044] The activity designer visually displays the design time visual representation of the activity The activity designer is a node in a designer hierarchy and may be themed or skinned The activity designer is hosted in a design environment (e g , an application program) and interacts with the host design environment via services Activity designer interfaces are described in detail in Appendix B The activity validator enforces the activity semantics at compile time as well as runtime The activity validator operates on the context of the workflow model and uses the services provided by the environment (e g , compiler, designer, or runtime) Validation occurs at various points in the hfecycle of a workflow Structural compliance checks are made when creating serialized representations of the workflow, when compiling, and m response to the user's request The semantic checks may be stronger at runtime than those performed at compile-time to ensure the safety of a runtime operation such as the addition or replacement of an activity in the activity tree of a running instance The invention evaluates semantics associated with each of the activities for conformance or compliance with, for example, predefined interface requirements Activity validation is described in detail in Appendix C
[0045] The activity senahzer is a component that serializes the metadata of an activity The activity senahzer is called from the various model/format senahzers The entire workflow model is serialized based on an extensible schema into a declarative markup language which may be further translated into other workflow languages as desired [0046] In one embodiment, the component model for an activity is stored as a data structure on a computer-readable medium In the data structure, the activity designer is represented by an image field storing data (e g , an icon) for visually representing the activity In addition, one or more author time fields store metadata defining properties,
methods, and events associated with the activity The activity senahzer is represented by a senahzer field storing data for transferring the metadata stored in the author time fields to a declarative representation of the activity The activity generator is represented by a business logic field storing software code associated with the metadata stored in the author time fields The activity executor is represented by an executor field storing data for executing the software code stored in the business logic field
Scopes and Schedules
[0047] The execution context of, and the shared data visible to, an executing activity is provided by a scope A scope is one of the core activities A scope is a unifying construct for bringing together variables and the state of a long-running service with transactional semantics, error-handling semantics, compensation, event handlers, and data state management A scope may have associated exception and event handlers In one embodiment, a scope may be transactional, atomic, long running, or synchronized Concurrency control is provided for the user in cases of conflicting read-write or wnte-wnte access to user variables A scope is also a transaction boundary, an exception handling boundary, and a compensation boundary Since scopes may be nested within a schedule, it is further possible to declare variables, messages, channels, and correlation sets with the same name in different scopes (even if the scopes are nested) without name collision [0048] Scopes nested within a schedule are only executable within the context of that schedule A schedule may be compiled either as an application (e g, a standalone executable entity) or as a library (e g , for invocation from other schedules) Every schedule that is compiled as a library effectively constitutes a new activity type that may be invoked from within other schedules A schedule's metadata includes the declaration of parameters [0049] Once a schedule is developed, instances of the developed schedule may be executed The process of activating and controlling a schedule instance is a function of the host environment in which the orchestration engine is embedded The orchestration engine provides a no-frills "simple host" that may be used to test schedules In addition, the orchestration engine provides an activation service to promote standardization of a "service provider" model (e g , application programming interfaces) that is used alike by the engine and external applications for interacting with the service environment (l e host) The activation service creates a schedule instance of a particular schedule type, optionally passing parameters The schedule instance is essentially a proxy to the running schedule instance and includes an identifier that uniquely identifies the instance, a reference to the
metadata (activity tree) for the schedule, and methods to suspend, resume, and terminate the instance The activation service also support finding a schedule instance based on a given schedule instance identifier
Code-Beside
[0050] A scope activity may have an associated code-beside class that includes business logic for the scope activity Since a schedule is itself a scope, a schedule may also have a code-beside class Any scopes nested within a schedule may also have their own code-beside classes The activities that are nested within a scope share the scope's code-beside class which acts as a container for their shared data state and business logic For example, metadata for a code activity includes a reference to a method with a particular signature in the code-beside In another example, metadata for a send activity includes an optional reference to a code-beside method of a particular signature plus mandatory references to a message declaration and a channel declaration
[0051] Exemplary uses of code-beside include the following declaration of variables, messages, channels, and correlation sets, declaration of m/out/ref parameters, declaration of additional custom properties, preparation of a message to be sent, processing of a message that has been received, implementation of a rule expressed in code that returns a Boolean value, manipulation of locally defined variables, reading activity metadata and instance data, writing activity instance data (e g , setting a property on an activity about to be executed), raising an event, throwing an exception, enumerating and navigating the hierarchy of activities in the running schedule instance's activity tree, including across nested scopes and schedule invocation boundaries, adding new activities to a composite activity within the running schedule instance, changing the declarative rules associated with activities within the running schedule instance, and obtaining references to, and manipulating, other running schedule instances
[0052] Referring to FIG 4, a block diagram illustrates an exemplary component model hfecycle A user interacts with computer-executable components stored on one or more computer-readable media The computer-executable components include a palette component 402 for presenting a plurality of activities, an interface component 404 for receiving a selection and hierarchical organization of the activities presented by the palette component 402, a declarative component 406 for serializing the activities received by the interface component 404 to create a persistent representation of the workflow, and a runtime component 408 for compiling the workflow representation serialized by the declarative
component 406 and the software code received by the interface component 404 into a single assembly containing an executable representation of the workflow The interface component 404 includes a user interface (e g , graphical) and/or an application programming interface (API) The user interacts with the computer-executable components to create workflow including code-beside and a serialized representation in a language such as an extensible object markup language (XOML) The runtime component 408 generates the assembly (e g , generated code, XOML, and code-beside) and executes the assembly The invention supports ad hoc modifications to the executing workflow, resulting in modified XOML
[0053] In another embodiment, the computer-executable components of the invention provide a schedule interface for creating a schedule associated with the workflow, a scope interface for creating a scope associated with the schedule, and an activity interface for selecting one or more activities The invention arranges the selected activities to create a workflow withm the created schedule for execution within the created scope The schedule interface, scope interface, and activity interface are application programming interfaces (APIs) in one embodiment
[0054] In a programmatic object model, compiling the plurality of activities arranged in the workflow includes receiving metadata, via a metadata interface, for each of the plurality of activities from the component model associated therewith Receiving the metadata includes receiving properties, methods, and events for each of the plurality of activities The method also validates the received metadata by examining semantics associated with the received metadata via a validate interface The method further generates software code associated with the received metadata via a code generator interface as a function of the validation The generated software code is compiled via a code compile interface One or more computer-readable media have computer-executable instructions for performing the method In one embodiment, the invention provides one or more of the metadata interface, the validate interface, the code generator interface, and the code compile interface
Workflow Stencils
[0055] A workflow stencil (e g , a workflow template or an activity package) includes a root activity and a set of activities Stencils may be domain and or host specific Examples of the former include a structured workflow stencil, human workflow stencil, and an unstructured workflow stencil Some stencils may be "closed" as a set of activities including one or more roots designed to work together, possibly in a particular host
environment Other stencils may be "open", to varying degrees A stencil defines its extensibility points For instance, a developer writes a CustomRoot and a new abstract CustomActivity and declares that the package is CustomRoot plus any activity that derives from CustomActivity
[0056] An exemplary BPEL or XLANG/S stencil includes a root activity with the following characteristics participates in state management and transactions, has associated event and exception handlers, supports contract first model, may be analyzed, and has well-defined activation and termination behavior The exemplary stencil further includes a set of messaging specific activities (e g , Send and Receive and their variants) and other structured activities such as Scope, Loop, Condition, Listen, and Throw [0057] An exemplary Halifax Stencil includes a root activity with the following characteristics implicit state management, associated exception handlers (0-n), supports event-based model, has well defined activation behavior, and has undefined termination The root activity contains 0-n EventDnven activities Each EventDnven Activity represents a Halifax Action Each EventDnven Activity has an associated state management protocol and executes m an atomic scope
Designer Framework (User Interface)
[0058] The orchestration engine provides a framework for designing various classes of workflow models in a WYSWYG fashion For example, referring to FIG 5, a high-level application user interface for authoring workflows relies upon wizards for specification of the workflow The framework includes a set of services and behaviors that enable developers to write visual workflow designers These services provide an efficient way of rendering a workflow process, support for Ink/Tablet for drawing the flows, and support for designer operations such as undo/redo, drag/drop, cut/copy/paste, zoom, pan, search /replace, bookmarks, adornments, smart tags for validation errors, valid drop-target indicators for activities, auto layout, view pagination, navigation markers, drag indicators, print and preview with headers/footers, etc Through such a user interface, simple workflows containing tasks and control flow composite activities (e g , sequence, parallel, and conditional) may be constructed No input of code (or reliance upon existing compiled code) is required either for rule specification (e g , conditional branching logic, while looping logic) or dataflow specification (e g , the output of task A is input to task B) The serialized representation of a schedule (including rules and dataflow) is self-contained and complete in some scenarios where no code-beside is required
[0059] Using the designer framework of the invention, the orchestration engine of the invention includes a rapid application development (RAD) style visual workflow designer with support for associating software code with the workflow model in a visual way Each activity in the workflow has an associated activity designer Each activity designer is written in terms of framework services The framework of the invention also contains a visual designer model The visual designer model includes a set of activity designers linked with one another via relationships described in the workflow model FIG 6 illustrates an exemplary workflow designer The invention includes various modes of associating code with the workflow model including "Code-Beside", "Code-Within" and "Code-Only" which enables round-tripping of the user code to the workflow model in real time The invention also provides real-time semantic errors while the user is building the workflow [0060] In one embodiment, the invention presents the user with a package identifying a plurality of activities in the designer framework user interface The invention further receives from the user a selection and hierarchical organization of the presented activities The invention serializes the received activities to create a persistent representation of the workflow The invention further receives from the user software code representing business logic for association with one of the plurality of activities in the workflow The invention may also receive a user-defined activity having one or more semantics associated therewith The invention includes a semantic checker or validator for evaluating the semantics for conformance to a predefined interface requirement If the semantics conform to the predefined interface requirement, the invention presents the user-defined activity as one of the plurality of activities The invention further compiles the software code to create one or more binary files For example, the invention complies the serialized workflow representation and software code into a single assembly containing an executable representation of the workflow The invention executes the created workflow In one embodiment, one or more computer-readable media have computer-executable instructions for performing the method
[0061] The orchestration engine designer allows the user to recursively compose higher order schedules by using other created schedule and using them The inline expansion of schedules allows the user to view the schedule contents inline and cut or copy the contents To enable the inline expansion of the schedule and to make the schedule read only, a separate design surface and designer host for the mime schedule is created Further, the composite schedule designer has its own hierarchy The invoked schedule is loaded and displayed when the designer is expanded by the user In one embodiment, the designer is
collapsed when the activity is dropped or copied on the design surface A property chains the calling activity designer with the root designer of the hosted schedule The following functions prevent the adding and removing of activities from the designer
internal static bool AreAllComponentsInWntableContext(ICollection components)
internal static bool IsContextReadOnly(IServiceProvider serviceProvider) [0062] These functions are called by the infrastructure to check if the context in which the activities are being inserted is writable For the hosted designer these functions return false In addition, properties are prevented from being modified Other functions fetch the activity designers from the appropriate components
internal static ServiceDesigner GetSafeRootDesigner(IServiceProvider serviceProvider)
internal static ICompositeActivityDesigner GetSafeParentDesigner(object obj)
internal static IActivityDesigner GetSafeDesigner(object obj) [0063] In one example, a user creates a schedule and compiles it as activity On successful compilation, the schedule appears on the toolbox The user opens or creates the schedule in which use of the compiled schedule is desired The user drags and drops the compiled schedule from the toolbox A collapsed schedule designer is shown on the design surface When the user wants to view the contents of the compiled schedule which was dropped, the user expands the schedule designer to show the contents of the invoked schedule inline in a read only state The lnhning of the called schedule enables the user to view the invoked schedule without switching between different schedule designers The feature is useful to developers composing higher order schedules by reusing existing schedules
Support for Customization of the Designer Framework using Themes/Skins [0064] A workflow designer written using the designer framework may be customized using workflow themes These may be extensible markup language (XML) files which declaratively describe various aspects of the designer The workflow designer provides wizard support for partners to extend activities Exemplary user interface features supported by the workflow designer include, but are not limited to, undo/redo, drag/drop, cut/copy/paste, zoom, pan, search/replace, bookmarks, adornments, smart tags for validation errors, valid drop-target indicators for activities, auto layout, view pagination, navigation markers, drag indicators, print and preview with headers/footers, and document outline integration The workflow designer supports custom designer themes/skins to enable
customizing the look and feel of the designer using XML metadata The workflow designer supports background compilation In one example, smart tags and smart actions are provided for validation errors while designing the schedule The workflow designer may be hosted in any container (e g , application programs, shells, etc )
[0065] An exemplary orchestration engine program includes a receive activity followed by a send activity The process receives a message and sends it out The user creates a project called "Hello World" and adds an orchestration item to the project The user then drags and drops a scope activity onto the design surface Next, the user drops a receive activity followed by a send activity onto the scope FIG 7 illustrates the resultant workflow 700 in the designer Each activity designer provides a user interface representation on an object model Developers are able to directly program the object model and set properties on activities or use the designer The orchestration engine designer allows a developer to select an activity from the toolbox and drag it onto the designer surface If the activity has already been placed into a schedule and needs to be moved, the developer is able to select it (by clicking on it) and drag it to the area of the schedule where it needs to go If a developer hold the control key while dragging and dropping, a copy of the selected activities selected are made
[0066] Active placement provides possible drop points (targets) as visual indicators on the design surface Auto scrolling also participates within the context of drag and drop When dealing with large schedules, navigation to areas of the designer currently not in the view port are accessible by dragging the activity towards the area of the schedule to be placed
[0067] Drag and drop is supported across schedules in the same project and across schedules in other projects in the same solution After an activity has been placed onto the design surface, the developer configures the activity Each activity has a set of properties that a developer configures in order for the schedule to be valid These properties are editable in the property browser Every activity controls what properties are viewable in the property browser To aide the developer in configuring various activities, the designer provides a variety of dialogs or "sub-designers" Each of the dialogs is invoked for various properties of activities
[0068] The orchestration engine is able to customize the activities presented in the toolbox When a developer creates a custom activity or schedule, the end result is an assembly Using a dialog, a developer is able to browse to the assembly location and select the assembly to make it appear as an orchestration engine activity Alternatively, a
developer may place the assembly in the orchestration engine installation path and it will be present as an orchestration engine activity
Application Programming Interfaces (APIs)
[0069] In another embodiment, the invention provides application programming interfaces (APIs) for performing various workflow operations The invention includes a design application programming interface for authoring the workflow The design application programming interface composes means for authoring a workflow and means for selecting one or more of the activities to create the workflow The invention also includes a compilation application programming interface for compiling the workflow authored via the design application programming interface The compilation application programming interface comprises means for serializing the workflow, means for customizing a visual appearance of the workflow, means for compiling the workflow authored via the design application programming interface, means for validating the workflow
[0070] The invention also includes a type provider application programming interface for associating a type with each of the activities in the workflow The type provider application programming interface comprises means for associating the type with each of the activities in the workflow and means for associating a type with each of the activities in the workflow
[0071] Appendix D describes exemplary APIs The APIs in Appendix D constitute exemplary means for authoring the workflow, exemplary means for selecting one or more of the activities to create the workflow, exemplary means for serializing the workflow, exemplary means for customizing a visual appearance of the workflow, exemplary means for validating the workflow, exemplary means for compiling the workflow, and exemplary means for associating a type with each of the activities in the workflow
Activity Execution Framework
[0072] With the exception of schedule and scope, the engine views activities as abstract entities and simply coordinates the execution of activities without knowing the specific data or semantics of any particular activity In one embodiment, four entities interact during the execution of an activity the activity itself, a parent activity of the activity that is executing, the scope enclosing the activity that is executing, and the orchestration engine Each entity has a different function
[0073] If the execute method of an activity returns without having signaled completion to its activity coordinator, the activity is said to be in a logical waiting state Such an activity may be cancelled by the orchestration engine, or continued (e g , once the item or event on which it is waiting becomes available or occurs, and the activity is notified of this by the engine)
[0074] Some activities which never enter the logical waiting state may never be cancelled Examples include the send activity and the code activity since they execute without any demands on external events or subscriptions Once handed a thread (l e once their execute method is called by the orchestration engine), these activities will do work until done The orchestration engine is never given an opportunity to cancel them since they do not return the thread until they signal completion [0075] The orchestration engine runtime uses rules to trigger events on which orchestration engine activities are executed The orchestration engine designer provides the user ability to associated rules to be evaluated at runtime to trigger events The orchestration engine designer enables the user to use different types of rules technology by providing extensibility architecture The designer is agnostic to the type of rules technology used
[0076] In one embodiment, the designer supports Boolean expression handlers as a way to associate a rule with an activity This means that in the user code file, the user writes a method which returns a true or false value, based on which the rule is triggered Currently there are multiple technologies which may also be used to evaluate rules including Info Agent and Business Rules Engine (BRE) To achieve this, the designer includes an extensibility architecture which enables the rule technology developers to host custom user interfaces in the designer The designer provides a way to the custom user interface writers to serialize the rules in the form of code statement collection The designer emits a Boolean handler in user code file with the code statement collections inserted into it The orchestration engine includes a default user interface which may also be used by the rule writers A rule technology provider add rules to the orchestration engine designer by creating a custom rule declaration, writing a user interface type editor associated with the custom rule declaration, creating a custom user interface to host the rules user interface, and generating code statements on save
[0077] In one example, a user selects the activity designer with which rule needs to be attached, locates the rule property in the property browser and selects the "RuleExpressionHandler" in the drop down (which makes the "Statements" property to
appear underneath the Rule Property in the user interface), specifies the user code method name in the "Statements" property, invokes a user interface type editor to invoke a dialog which will host rules specific user interface, and defines rules in the dialog by creating new predicate rows and grouping them together The user interface emits a method in the user code file The method name will be same as the one specified by the user in the property browser The code statements equivalent to creating the rule will be inserted in the user code method for rule
Messaging During Execution
[0078] In a running workflow, messages sent to a schedule are intended for a specific schedule instance For example, an invoice for purchase order #123 must be sent back to the same schedule instance that originated (e g , sent out) that purchase order To match an inbound message with the appropriate schedule instance, the message and the schedule instance share a correlation set The correlation set may be a single-valued correlation set in which means an identifier field in the message is matched against an identifier of the same type that is held by schedule instances Multi-property correlation sets are also possible and analogous to multi-column primary keys m a database table
[0079] The correlation set value held by a schedule instance is initialized when the schedule instance sends out a message (e g , the value may be taken from an identifier field of an outbound purchase order) or receives a message This correlation set value is then a part of that schedule instance's state When a subsequent inbound message arrives, the correlation set value held in the schedule instance state is matched against the identifier held by an inbound message of the expected type When a match is found, the correlation set is satisfied and the message is delivered to the schedule instance
[0080] Although the implementation of correlation sets is a function of the orchestration engine and host environment, the user in one embodiment declares the correlation sets to make the schedule instance work correctly In another embodiment, some activities (e g , SendRequest/ReceiveResponse activities and ReceiveRequest/SendResponse activities) set up the correlation sets independent of the user A wide range of validation checks are performed by the send and receive activities to ensure that correlation sets are initialized and followed properly
Dynamic Editing of Executing Workflows
[0081] The orchestration engine provides a framework for authoring (and subsequently
visualizing and executing) various types of workflows Examples include event-condition-
action (ECA) style workflows or structured flows or rules driven flows Further, regardless of the way the workflow was modeled, the framework allows the users to author or edit workflows in the same manner at design time or even when the workflow process is running without the need for recompiling the workflow process The framework allows the user to roundtnp between the runtime and the design time representation with hi-fidelity Ad hoc changes are the changes made at run time to the process model A user may ask a running instance for its schedule model and make changes to the model For example, the user may add, remove, or replace activities m a batch, then commit or rollback the batched changes In one embodiment, the model is validated after the updates In many workflow scenarios of the invention, there is a blurring of, or even an elimination of, the separation between "design-time authoring" and "runtime execution "
[0082] A schedule instance effectively shares with other instances the activity type (metadata) tree defined for those instances' schedule type But any schedule instance, once it begins executing, may be changed on the fly via the addition of new activities or the manipulation of declarative rules It is possible to take such a modified schedule instance and "save as" as a new schedule type or more generally, to simply recover the serialized representation from the instance That is, a running schedule instance may be serialized and then brought into any designer (e g, authoring environment) or runtime visualization tool [0083] Further, it is possible for an advanced developer to author a schedule entirely as software code To author a schedule type directly, the developer simply includes a static method called InitiahzeScheduleModel in the software code in the code-beside class for the schedule and marks this method with a [ScheduleCreator] attribute In one embodiment, the static method takes no parameters and returns a Schedule object There is no companion serialized file, though the serialized representation of the schedule may be recovered from the Schedule object that is created Although this means that a schedule may be developed using a single software code file, validation checks may not be performed on the file The orchestration engine compilation ensures the structural and semantic validity of the activity tree that underlies the schedule type In another embodiment, compilation and validation run internally to produce the actual type that is executed, but no code input is required Schedule type compilation becomes a very light process since there is no translation from a compile-time object model to a runtime object model In essence, compilation simply combines the object model representation of a schedule with code-beside to produce a new type In one embodiment, there may be no fundamental need to provide any code-beside at all for a particular schedule if the compiled code-beside matches what is demanded by the
activities in the object model or code-beside may already exist in compiled form (an
assembly)
[0084] When compiling a serialized schedule, it is possible to point to an existing
compiled type that effectively serves as the code-beside for the schedule A derivative of
this compiled type is created and this new type serves as the code-beside to ensure that a
unique type is created to represent the new schedule
Serialization Architecture
[0085] The serialization infrastructure provides a modular, format neutral and easily extensible mechanism to serialize the orchestration engine activity tree FIG 8 illustrates the serialization of objects in a graph
[0086] In particular, a caller (e g , an application program or a user) requests a senahzer for an object (or activity) A from the serialization manager The metadata attribute of object A's type binds object A to a senahzer of the requested type The caller then asks the senahzer to serialize object A Object A's senahzer then serializes object A For each object encountered while serializing, the senahzer requests additional senahzers from the serialization manager The result of the serialization is returned to the caller [0087] Every activity in the orchestration engine component model may participate in serialization The senahzer component is not a part of activity class itself in one embodiment Instead, the component is specified by annotating a senahzer attribute in a class associated with the activity The senahzer attribute points to a class which is used to serialize objects of that activity type In another embodiment, provider components for an activity type ovemde the default senahzer provided by the activity [0088] Designer serialization is based upon metadata, senahzers, and a serialization manager Metadata attnbutes are used to relate a type with a senahzer A "bootstrapping" attribute may be used to install an object that provides senahzers for types that do not have them A senahzer is an object that knows how to serialize a particular type or a range of types There is a base class for each data format For example, there may be an XmlSenahzer base class that knows how to convert an object into XML The mvention is a general architecture that is independent of any specific serialization format The senahzation manager is an object that provides an information store for all the various senahzers that are used to senahze an object graph For example, a graph of fifty objects may have fifty different senahzers that all generate their own output The senahzation manager may be used by these senahzers to communicate with each other when necessary
[0089] In one embodiment, the use of serialization providers coupled with senahzers that use generic object metadata provide a callback mechanism where an object is given the opportunity to provide a senahzer for a given type A serialization manager may be given a serialization provider through a method such as AddSenahzationProvider A serialization provider may be automatically added to a serialization manager by adding an attribute such as DefaultSenalizationProviderAttnbute to the senahzer
[0090] In one embodiment, the format is dictated by the following rules an object is serialized as an xml element, a property of an object is categorized as simple property (e g, serialized as an xml attribute) or complex property (serialized as child element), and a child object of an object is serialized as child element The definition of a child object may differ from an object to another object The example below is the serialization of a while activity, which has a Send activity as one of its child objects

[0091] In an embodiment in which the language used for serialization is XOML, each XOML element is serialized to its respective object when the schedule is compiled Objects include both simple and complex types The mapping between the XOML representation of each activity and its mapping to the authoring object model is next described Serialization of XOML varies between Primitive and Composite activities
[0092] Simple types for primitive activities are serialized as attributes on the activity type Complex types for primitive activities are serialized as child elements As an example, here is the XOML representation of a Send activity

[0093] In a similar manner to primitive type serialization, simple types for composite activities are serialized as attributes on the activity type However, by definition, composite activities encapsulate nested activities Each nested activity is serialized as another child element As an example, here is the XOML representation of a While activity

[0094] A strong relationship between the process/workflow view and the serialized representation exists FIG 9 illustrates a schedule definition and the relationship between a visual workflow, a serialized (e g , XOML) representation of the workflow, and the code beside of the workflow When authoring in either representation, the other will incur changes Thus, modifying the XOML for an activity (or its constituent parts in cases of composite activities) is directly reflected in the process/workflow view when a developer switches between the two The converse is also applicable Modifying the activity in the process/workflow view results in the appropriate modification within XOML As an example, the deletion of an activity in the process/workflow view results in the removal of the XML element in XOML for the same activity Round tripping also occurs between the process/workflow view and the code beside
[0095] During creation of the XOML code, if the XOML definition does not conform to a pre-defined interface requirement, the offending XML element is underscored or otherwise visually identified to the developer If the developer switches to the process view, they will be alerted that there is an error within the XOML and the designer provide a link where the developer may click and will be navigated to the offending element This same error appears in the task pane and upon doubling clicking on the error, the developer will be navigated to the offending element in the XOML
Creating the Activity Tree from a XOML File ("Deserialization')
[0096] In one embodiment, a CreateEditorInstance() function creates a DesignSurface object and then calls a BeginLoad() function onto the DesignSurface object passing the actual loader object into it, which eventually ends up in a BeginLoad() call to a DesignerLoader() function A PerformLoad() function reads the text buffer object and deserializes it to the orchestration engine component model hierarchy The invention walks through the hierarchy and inserts the activities into the design surface to load the components in the visual studio
[0097] The invention also listens to changes to the XOML file to track the hierarchy and item identification changes to update the values in the visual studio cache A secondary document data list includes a list of secondary documents, invisible to the user, on which orchestration engine designer works For example, it is possible that user has not opened the code beside file, but when the user makes changes in the orchestration engine designer, the changes are made to the code beside file As this file is not visible to the user, the file is maintained as a secondary document Whenever the XOML file is saved, the secondary documents are automatically saved If the name of one of these files changes or if the file is deleted, the invention updates the corresponding secondary document objects accordingly [0098] Exemplary deserialization guidelines for an object tree are as follows An xml element is first treated as a property of parent object If the parent object does not have a property with the element's tag name then the element is treated as a child object of the parent object An xml attribute is treated as simple property on the parent object [0099] In an exemplary deserialization using the serialized code above, a element is treated as an object created using the xml namespace information A element is treated as a property of the While activity The element is treated an as object whose value will be applied to the ConditionRule property The element is first tried as a property of the While activity, but the 'While' activity does not have a property with the name 'Send', so the element is treated as an object and added as the children activity of the while activity The element is treated as a property of the Send activity Because the Message property on Send is read only, the contents of Message element are considered as the contents of Message object A similar rule applies to the deserialization of and elements
[0100] Under the following conditions, XOML de-serialization will critically fail the XOML code is not well formed, the XomlDocument is not the first element in the XOML code, and the first activity in the XOML code cannot be de-serialized The developer will
be presented with error message with which they may navigate to the offending XML element when switching from XOML view to process/workflow view
Hosting the Orchestration Engine Designer
[0101] The designer framework may be hosted in any application program This is a very useful feature for third party applications to render workflow in their respective environments It also will allow third parties to develop tools around the orchestration engine designer by rehosting and customizing the design surface The framework of the invention expects the hosting container application to provide a set of services such as editors and/or text buffers
[0102] One step in rehosting the designer is to create a loader and a design surface The loader is responsible for loading a XOML file and constructing the designer host infrastructure which maintains the activities The design surface maintains the designer host infrastructure within it and provides services to host and interact with the design surface The design surface acts as a service container as well as a service provider In one example, the following code is executed to load a XOML document and construct a designer host which maintains the activities in it
this loader XomlFile = filePath,
if (this surface IsLoaded == false)
this surface BeginLoad(this loader), [0103] The following services enable different functions in the designer An ISelectionService function maintains the selected objects An IToolboxService function manages interaction with the toolbox An IMenuCommandService function manages interaction with the menu An ITypeProvider function enables the type system In addition, there may be additional services provided by the designer hosting environment to enable advanced designer features
[0104] The type system is a component in the component model framework of the invention When a designer is hosted inside a project system, a TypeProvider object is created on a per project basis Assembly references in the project are pushed to the type provider Further, the user code files in the project are parsed and a single code compile unit is created and pushed to the type provider In addition, the invention listens to the events in the project system which may cause the types to be changed in the type system and makes appropriate calls to the type provider to re-load types in response to the changes
Undo/Redo
[0105] After creating and correctly constructing a schedule, a developer may wish to rollback a series of performed operations Undo and redo functions of the invention provide visual feedback illustrating which activity has been directly affected For example, when a property change on an activity is undone, the activity which was affected becomes selected When the deletion of multiple objects is undone, all the objects involved become selected when they are restored to the schedule Undo/Redo is a common feature used throughout many applications in other fields and its meaning is well understood In the orchestration engine designer, undo/redo items are not purged on Save Further, undo/redo may be performed in the process/workflow view, XOML view, when a developer switches between views, and in the code beside
[0106] Undo/Redo is provided for the following actions in the process/workflow view activity drag and drop (e g , dragging an activity from the toolbox to the design surface, moving an activity from one part of the schedule to another, and moving an activity from one designer to another), configuration of an activity (e g , specifying properties for an activity), and cut/copy/paste/delete
[0107] In one embodiment, the serialized view (e g , XOML view) is an XML editor which provides the standard undo/redo operations of a text editor The designer of the invention provides feedback to the developer indicating that changes made in the process/workflow view and then undone in serialized view will result in the loss of serialized code When the developer constructs a portion of the schedule in the process/workflow view, switches to the serialized view and then decides to perform an undo/redo operation, a warning will appear
Exemplary Operating Environment
[0108] FIG 10 shows one example of a general purpose computing device in the form of a computer 130 In one embodiment of the invention, a computer such as the computer 130 is suitable for use in the other figures illustrated and described herein Computer 130 has one or more processors or processing units 132 and a system memory 134 In the illustrated embodiment, a system bus 136 couples various system components including the system memory 134 to the processors 132 The bus 136 represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures By way of example, and not limitation, such architectures include Industry
Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus also known as Mezzanine bus [0109] The computer 130 typically has at least some form of computer readable media Computer readable media, which include both volatile and nonvolatile media, removable and non-removable media, may be any available medium that may be accessed by computer 130 By way of example and not limitation, computer readable media comprise computer storage media and communication media Computer storage media include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data For example, computer storage media include RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store the desired information and that may be accessed by computer 130 Communication media typically embody computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a earner wave or other transport mechanism and include any information delivery media Those skilled in the art are familiar with the modulated data signal, which has one or more of its characteristics set or changed in such a manner as to encode information in the signal Wired media, such as a wired network or direct-wired connection, and wireless media, such as acoustic, RF, infrared, and other wireless media, are examples of communication media Combinations of any of the above are also included within the scope of computer readable media [0110] The system memory 134 includes computer storage media in the form of removable and/or non-removable, volatile and/or nonvolatile memory In the illustrated embodiment, system memory 134 includes read only memory (ROM) 138 and random access memory (RAM) 140 A basic input/output system 142 (BIOS), containing the basic routines that help to transfer information between elements within computer 130, such as during start-up, is typically stored m ROM 138 RAM 140 typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit 132 By way of example, and not limitation, FIG 10 illustrates operating system 144, application programs 146, other program modules 148, and program data 150 [0111] The computer 130 may also include other removable/non-removable, volatile/nonvolatile computer storage media For example, FIG 10 illustrates a hard disk
drive 154 that reads from or writes to non-removable, nonvolatile magnetic media FIG 10 also shows a magnetic disk drive 156 that reads from or writes to a removable, nonvolatile magnetic disk 158, and an optical disk drive 160 that reads from or writes to a removable, nonvolatile optical disk 162 such as a CD-ROM or other optical media Other removable/non-removable, volatile/nonvolatile computer storage media that may be used in the exemplary operating environment include, but are not limited to, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like The hard disk drive 154, and magnetic disk drive 156 and optical disk drive 160 are typically connected to the system bus 136 by a non-volatile memory interface, such as interface 166
[0112] The drives or other mass storage devices and their associated computer storage media discussed above and illustrated in FIG 10, provide storage of computer readable instructions, data structures, program modules and other data for the computer 130 In FIG 10, for example, hard disk drive 154 is illustrated as storing operating system 170, application programs 172, other program modules 174, and program data 176 Note that these components may either be the same as or different from operating system 144, application programs 146, other program modules 148, and program data 150 Operating system 170, application programs 172, other program modules 174, and program data 176 are given different numbers here to illustrate that, at a minimum, they are different copies [0113] A user may enter commands and information into computer 130 through input devices or user interface selection devices such as a keyboard 180 and a pointing device 182 (e g , a mouse, trackball, pen, or touch pad) Other input devices (not shown) may include a microphone, joystick, game pad, satellite dish, scanner, or the like These and other input devices are connected to processing unit 132 through a user input interface 184 that is coupled to system bus 136, but may be connected by other interface and bus structures, such as a parallel port, game port, or a Universal Serial Bus (USB) A monitor 188 or other type of display device is also connected to system bus 136 via an interface, such as a video interface 190 In addition to the monitor 188, computers often include other peripheral output devices (not shown) such as a printer and speakers, which may be connected through an output peripheral interface (not shown)
[0114] The computer 130 may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer 194 The remote computer 194 may be a personal computer, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements
described above relative to computer 130 The logical connections depicted in FIG 10 include a local area network (LAN) 196 and a wide area network (WAN) 198, but may also include other networks LAN 136 and/or WAN 138 may be a wired network, a wireless network, a combination thereof, and so on Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets, and global computer networks (e g , the Internet)
[0115] When used in a local area networking environment, computer 130 is connected to the LAN 196 through a network interface or adapter 186 When used in a wide area networking environment, computer 130 typically includes a modem 178 or other means for establishing communications over the WAN 198, such as the Internet The modem 178, which may be internal or external, is connected to system bus 136 via the user input interface 184, or other appropriate mechanism In a networked environment, program modules depicted relative to computer 130, or portions thereof, may be stored in a remote memory storage device (not shown) By way of example, and not limitation, FIG 10 illustrates remote application programs 192 as residing on the memory device The network connections shown are exemplary and other means of establishing a communications link between the computers may be used
[0116] Generally, the data processors of computer 130 are programmed by means of instructions stored at different times in the various computer-readable storage media of the computer Programs and operating systems are typically distributed, for example, on floppy disks or CD-ROMs From there, they are installed or loaded into the secondary memory of a computer At execution, they are loaded at least partially into the computer's primary electronic memory The invention described herein includes these and other various types of computer-readable storage media when such media contain instructions or programs for implementing the steps described below in conjunction with a microprocessor or other data processor The invention also includes the computer itself when programmed according to the methods and techniques described herein
]0117] For purposes of illustration, programs and other executable program components, such as the operating system, are illustrated herein as discrete blocks It is recognized, however, that such programs and components reside at various times in different storage components of the computer, and are executed by the data processor(s) of the computer [0118] Although described in connection with an exemplary computing system environment, including computer 130, the invention is operational with numerous other general purpose or special purpose computing system environments or configurations The

computing system environment is not intended to suggest any limitation as to the scope of use or functionality of the invention Moreover, the computing system environment should not be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary operating environment Examples of well known computing systems, environments, and/or configurations that may be suitable for use with the invention include, but are not limited to, personal computers, server computers, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, mobile telephones, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like
[0119] The invention may be described in the general context of computer-executable instructions, such as program modules, executed by one or more computers or other devices Generally, program modules include, but are not limited to, routines, programs, objects, components, and data structures that perform particular tasks or implement particular abstract data types The invention may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices
[0120] An interface in the context of a software architecture includes a software module, component, code portion, or other sequence of computer-executable instructions The interface includes, for example, a first module accessing a second module to perform computing tasks on behalf of the first module The first and second modules include, in one example, application programming interfaces (APIs) such as provided by operating systems, component object model (COM) interfaces (e g , for peer-to-peer application communication), and extensible markup language metadata interchange format (XMI) interfaces (e g , for communication between web services)
[0121] The interface may be a tightly coupled, synchronous implementation such as in Java 2 Platform Enterprise Edition (J2EE), COM, or distributed COM (DCOM) examples Alternatively or m addition, the interface may be a loosely coupled, asynchronous implementation such as in a web service (e g , using the simple object access protocol) In general, the interface includes any combination of the following characteristics tightly coupled, loosely coupled, synchronous, and asynchronous Further, the interface may
conform to a standard protocol, a proprietary protocol, or any combination of standard and
proprietary protocols
[0122] The interfaces described herein may all be part of a single interface or may be
implemented as separate interfaces or any combination therein The interfaces may execute
locally or remotely to provide functionality Further, the interfaces may include additional
or less functionality than illustrated or described herein
[0123] The order of execution or performance of the methods illustrated and described
herein is not essential, unless otherwise specified That is, elements of the methods may be
performed m any order, unless otherwise specified, and that the methods may include more
or less elements than those disclosed herein For example, it is contemplated that executing
or performing a particular element before, contemporaneously with, or after another element
is within the scope of the invention
[0124] When introducing elements of the present invention or the embodiment(s)
thereof, the articles "a," "an," "the," and "said" are intended to mean that there are one or
more of the elements The terms "comprising," "including," and "having" are intended to
be inclusive and mean that there may be additional elements other than the listed elements
[0125] In view of the above, it will be seen that the several objects of the invention are
achieved and other advantageous results attained
[0126] As various changes could be made in the above constructions, products, and
methods without departing from the scope of the invention, it is intended that all matter
contained in the above description and shown in the accompanying drawings shall be
interpreted as illustrative and not in a limiting sense
APPENDIX A
Exemplary Activities and Exemplary Implementation Thereof
[0127] Exemplary activities include the following Send, SendRequest, SendResponse, Receive, ReceiveRequest, ReceiveResponse, Code, Delay, Fault, Suspend, Terminate, InvokeSchedule, InvokeSchedules, InvokeWebService, DotNetEventSource, DotNetEventSmk, Sequence, Parallel, While, ConditionalBranch, Conditional, Constrained, ConstramedActivityGroup (CAG), EventDnven, Listen, EventHandlers, ExceptionHandler, ExceptionHandlers, Compensate, CompensationHandler, Scope, and Schedule [0128] The activity classes listed above rely upon a set of supporting types for their metadata declarations These types include DataElement, LiteralElement, MemberDeclaration, VanableDeclaration, TypedVanableDeclaration, MessageDeclaration, CorrelationSetDeclaration, ChannelDeclaration, TypedChannelDeclaration, HandlerDeclaration, TypedHandlerDeclaration, RuleDeclaration, CodeExpressionRuleDeclaration, DeclarativeExpressionRuleDeclaration, ParameterDeclaration, ParameterDeclarationCollection, ParameterBinding, and ParameterBmdingCollection
[0129] Additionally, there are a set of standard delegate types defined that map to the types of the code-beside methods that certain activities require as metadata In addition, there are a set of utility classes that support serialization [XomlSenahzer and related types] and compilation [XomlCompiler and related types] of schedules There is a utility wfc exe (e g , "workflow compiler"), that is a command line tool for compiling schedules
Send Activities
[0130] The orchestration engine provides three activities for sending messages, each of which addresses a different use case Additionally, because the three activities share some metadata, an abstract base class is defined and used as the superclass of all three
SendBase Metadata
■ A message reference
■ An optional code-beside method
■ An optional collection of correlation sets
Send Metadata
o A message reference
o An optional code-beside method
o An optional collection of correlation sets
■ An outbound channel reference, which may be untyped or typed If the channel is
typed, an operation is also specified on the channel declaration
Execution
A Send activity sends the specified message on the specified channel If a typed channel is used, the Send activity utilizes a specific operation This operation must be defined to return void An untyped channel accepts messages of any type Before the message is sent, an optional code-beside handler is invoked The normal usage of this handler is to initialize or otherwise prepare the message that is about to be sent The Send activity also initializes any correlation sets that have been specified Send activities do not follow correlation sets Send executes in a synchronous manner (it does not yield its thread until it is complete)
SendRequest
Purpose Send a request message as part of a request-response message pattern
Metadata
o A message reference
o An optional code-beside method
o An optional collection of correlation sets
■ An outbound channel reference, which may be untyped or typed If the channel is
typed, an operation is also specified
Execution
A SendRequest activity sends the specified message on the specified channel If a typed channel is used, the Send activity utilizes a specific operation This operation must be defined to return a type other than void (Note this is how SendRequest differs from Send) An untyped channel accepts messages of any type Before the message is sent, an optional code-beside handler is invoked The normal usage of this handler is to initialize or otherwise prepare the message that is about to be sent The SendRequest activity also initializes any correlation sets that have been specified In a simple schedule that only contains a SendRequest/ReceiveResponse pair and no other receive activities, no correlation
sets need to be explicitly created or initialized, correlation of request and response messages will be performed automatically Send activities do not follow correlation sets SendRequest executes in a synchronous manner (it does not yield its thread until it is complete)
SendResponse
Purpose Send a response message as part of a request-response message pattern
Metadata
o A message reference
o An optional code-beside method
o An optional collection of correlation sets
■ The ID of a ReceiveRequest activity
Execution
A SendResponse activity sends the specified message on the channel that is declared on the associated ReceiveRequest activity If a typed channel is used, the SendResponse activity utilizes the operation indicated by the ReceiveRequest activity This operation must be defined to return a type other than void An untyped channel accepts messages of any type Before the message is sent, an optional code-beside handler is invoked The normal usage of this handler is to initialize or otherwise prepare the message that is about to be sent The SendResponse activity also initializes any correlation sets that have been specified Send activities do not follow correlation sets SendResponse executes in a synchronous manner (it does not yield its thread until it is complete)
Receive Activities
The orchestration engine provides three activities for receiving messages, each of which addresses a different use case Additionally, because the three activities share some metadata, an abstract base class is defined and used as the superclass of all three ReceiveBase
Purpose Abstract base class for receive activities Metadata
■ A message reference
■ An optional code-beside method
■ An optional collection of correlation sets
Receive
Purpose Receive a message
Metadata
o A message reference
o An optional code-beside method
o An optional collection of correlation sets
■ A Boolean indicating whether this is an activating receive
■ An inbound channel reference, which may be untyped or typed If the channel is typed, an operation is also specified
Execution
A Receive activity performs a blocking wait for the arrival of a message on the specified channel If a typed channel is used, the Receive awaits the arrival of a message of a specific type on a specific operation of the channel This operation must be defined to return void An untyped channel delivers messages of any type If the Receive is an activating receive, a special subscription will be configured so that the arrival of a message on the indicated channel will cause a new instance of the schedule of which the Receive is part to be created and executed Correlation sets to be followed by the Receive are used in the message subscription that is set up on the channel This ensures that a schedule instance receives only those messages that are intended for that instance After receiving the message, the Receive activity initializes any correlation sets that have been specified as requiring initialization Then, an optional code-beside handler is invoked The normal usage of this handler is to process the message in some manner
ReceiveRequest
Purpose Receive a request message as part of a request-response message pattern
Metadata
o A message reference
o An optional code-beside method
o An optional collection of correlation sets
■ A Boolean indicating whether this is an activating receive
■ An inbound channel reference, which may be untyped or typed If the channel is typed, an operation is also specified
Execution
A ReceiveRequest activity performs a blocking wait for the arrival of a message on the specified channel If a typed channel is used, the ReceiveRequest awaits the arrival of a message of a specific type on a specific operation of the channel This operation must be defined to return a type other than void (this is how ReceiveRequest differs from Receive) An untyped channel delivers messages of any type If the ReceiveRequest is an activating receive, a special subscription will be configured so that the arrival of a message on the indicated channel will cause a new instance of the schedule of which the ReceiveRequest is part to be created and executed Correlation sets to be followed by the ReceiveRequest are used in the message subscription that is set up on the channel This ensures that a schedule instance receives only those messages that are intended for that instance After receiving the message, the ReceiveRequest activity initializes any correlation sets that have been specified as requiring initialization Then, an optional code-beside handler is invoked The normal usage of this handler is to process the message in some manner In a simple schedule that only contains a ReceiveRequest/SendResponse pair and no other receive activities, no correlation sets need to be explicitly created or initialized, correlation of request and response messages will be performed automatically
ReceiveResponse
Purpose Receive a response message as part of a request-response message pattern
Metadata
o A message reference
o An optional code-beside method
o An optional collection of correlation sets ■ The ID of a SendRequest activity Execution
A ReceiveResponse activity performs a blocking wait for the arrival of a message on the channel specified on the associated SendRequest activity If a typed channel is used, the ReceiveResponse activity utilizes the operation indicated by the SendRequest activity This operation must be defined to return a type other than void An untyped channel delivers messages of any type ReceiveResponse activities do not follow correlation sets After the message is received, an optional code-beside handler is invoked The normal usage of this handler is to process the message that has been received After receiving the message, the ReceiveResponse activity initializes any correlation sets that have been
specified as requiring initialization Then, an optional code-beside handler is invoked The normal usage of this handler is to process the message in some manner
Code
Purpose Execute a method implemented in code-beside
Metadata
■ A code-beside method
Execution
The Code activity executes the code-beside method indicated in the metadata Code executes in a synchronous manner (it does not yield its thread until it is complete) Thus, the execution of the code-beside method is expected to be performed and should not block with a dependency on some external resource For example, this code should typically not invoke a web service The normal use of the Code activity is to inspect schedule instance state and manipulate local variables and messages
Delay
Purpose Wait until a specific DateTime in the future is reached
Metadata
■ A code-beside method that returns a DateTime
Instance Data
■ The DateTime value that the Delay is waiting (or has waited) until This value is
reported as null until the Delay actually begins executing
Execution
The Delay activity executes its mandatory code-beside method to generate a DateTime value It internally sets the Timeout Value property on its instance data to this value If the DateTime is in the past, the Delay completes immediately Otherwise, it sets up a timer subscription so that the Delay will be notified when the timer fires When the timer fires, the Delay is notified and it completes Like a receive activity, Delay does not complete its execution synchronously, instead, it yields its thread and awaits notification that the DateTime has been reached
Based on the characteristics of the underlying timer service surfaced by the engine, the Delay activity is guaranteed to complete no sooner than the indicated DateTime, but, it may in fact take longer since the timer notification may occur some time after the DateTime is reached (for example, due to high system stress in a server environment) Note that a UTC
time must be returned in order for the Delay to work as expected, for many cases, this means using DateTime UtcNow instead of DateTime Now in the code handler that returns the DateTime value
Fault
Purpose Throw an exception
Metadata
■ A code-beside method that returns an Exception
Execution
The Fault activity executes its mandatory code-beside method to generate an Exception object It then throws this exception Functionally, the Fault activity is equivalent to a Code activity whose code beside method simply throws the exception that is created by the ExceptionProvider The purpose of Fault is to capture the throwing of business exceptions as part of the process metadata for a schedule Due to the fact that it throws an exception, the Fault activity will have a reported Outcome of Faulted, despite the fact that this constitutes normal execution of this activity
Suspend
Purpose Suspend the running schedule instance
Metadata
■ An error message to report to administrators
Execution
The Suspend activity suspends the current schedule instance What this means is that the engine immediately stops handing the thread to any items queued up for the instance that has been suspended, no 'Cancel' signal occurs The host (e g , instance manager and persistence provider) decides where the error message goes
Terminate
Purpose Terminate the running schedule instance
Metadata
■ An error message to report to administrators
Execution
The Terminate activity terminates the current schedule instance What this means is that, as with Suspend, the engine immediately stops handing the thread to items queued up for the
instance that has been terminated With Terminate, the queued items are also deleted since there is no possibility of the instance being resumed As with Suspend, no 'Cancel' signal occurs The host (e g , instance manager and persistence provider) decide where the error message goes
Invoke Schedule
Purpose Invoke a schedule
Metadata
• The type of the schedule to be invoked
• An enum that indicates whether the invocation has CALL or EXEC semantics
• A set of parameter bindings
• An optional code-beside method that is called before the schedule is invoked Execution
The InvokeSchedule activity first calls the OnlmtiahzeCallee code-beside method, if one has been specified Typically, this method will be used to set up In parameters for the schedule instance to be invoked InvokeSchedule then creates and invokes a schedule instance of the specified type, passing the parameters that have been provided The InvokeSchedule activity blocks (and yields its thread) if the invocation semantic is CALL, and waits for the called schedule to complete Alternatively, the InvokeSchedule activity completes immediately once the schedule instance is invoked, if the invocation semantic is EXEC The InvokeSchedule calls the OnCompletedCallee code-beside method, if one has been specified Typically, this method will process the Out parameters for the schedule instance that was invoked
Invoke Web Service Purpose Invoke a web service Metadata
• The name of the proxy class that is used to invoke the web service
• The name of the method on the web service to be invoked
• A Boolean indicating whether the invocation is synchronized
• A set of parameter bindings Execution
Invokes a web service via a proxy class, passing and receiving parameters as specified
DotNetEvent Sink
Purpose Model the handling of an event that is raised via the RaiseEvent method or
DotNetEventSource activity within a previously invoked (child) schedule
Metadata
• A method in code-beside that is of the same type as the delegate indicated in the
raising of the event to be handled
Instance Data None beyond ActivityState
Execution
Blocks awaiting notification that the specified event has been raised by a previously
invoked schedule instance The invoked schedule instance must be running under CALL
semantics
DotNetEvent Source
Purpose Model the raising of an event that is functionally equivalent to raising the event in
code-beside via the RaiseEvent method
Metadata
• A delegate type, indicating the type of event that is being raised (and the type of the
handler that is required to handle the event)
• Parameter bindings to the method parameters defined on the delegate type
Execution
Raises the specified event, and immediately completes execution There is no guarantee as to the number of subscribers to this event (there may be zero or more), and neither is there any mechanism for getting data back from the potential handler(s) of this event, 1 e the semantic is fire-and-forget
Sequence
Purpose Execute a set of child activities according to a single defined ordering
Execution
The Sequence activity coordinates the execution of a set of child activities in an ordered
fashion, one at a time The Sequence completes when the final child activity completes
Parallel
Purpose Execute a set of child activities concurrently
Execution
The Parallel activity executes a set of child activities concurrently The order in which the children are enabled for execution is non-deterministic The Parallel completes when all child activities are complete Due to the threading model of the orchestration engine, in actuality only one activity within a Parallel may be executing at a given point in time
While
Purpose Iteratively execute a child activity
Metadata
• A rule that governs the iteration
Execution
Iteratively executes the child activity Prior to each iteration (including the first), the rule is evaluated, if it evaluates to false, then the While activity completes
ConditionalBranch
Purpose Represent a branch of a Conditional
Metadata
• A rule that governs the conditional execution of the wrapped activity (branch)
Execution
Executes the child activities, per Sequence semantics The parent Conditional activity is responsible for examining the metadata (rule) to determine whether the ConditionalBranch should be executed The Conditional activity itself offers no additional properties (other than ID and Description) However, Conditionals are comprised of conditional branches which expose properties Upon selection of a ConditionalBranch, two addition context menu operations appear Move Left (moves the selected ConditionalBranch to its immediate left in the conditional) and Move Right (moves the selected ConditionalBranch to its immediate right in the conditional)
Conditional
Purpose Conditionally execute one of n ConditionalBranch activities
Execution
A Conditional activity contains an ordered set of ConditionalBranch activities The
Conditional executes the first ConditionalBranch activity whose rule evaluates to TRUE
The final ConditionalBranch activity is permitted to not specify a rule, in which case it is
always considered to evaluate to TRUE It is possible for a Conditional to complete without having executed any child activity Essentially, this provides IF-ELSEIF-ELSE semantics
Constrained
Purpose Wrap an activity for the purpose of adding it to a CAG
Metadata
• An enable rule for the wrapped activity
• A disable rule for the wrapped activity Runtime Properties
• Integer indicating whether the wrapped activity has completed at least once Execution
The only allowed parent of a constrained activity is a CAG The CAG itself utilizes the
enable and disable rules on a constrained activity to determine when to execute it When
the Constrained activity is told by the CAG to execute, it simply executes the activity that it
wraps
The Performed property is incremented when the constrained activity completes its
execution It is reset to zero only when the parent CAG itself is re-executed (e g within a
WhileLoop or a second, outer, CAG)
CAG (Constrained Activity Group)
Purpose Provide constraint-based execution of a set of child Constrained activities
Metadata
• A completion rule
Execution
CAG contains only constrained activities When the CAG executes, it executes (and re-executes) child activities based upon the evaluation of their enable and disable constraints A child activity is executed by the CAG only when its enable rule evaluates to true and its disable rule evaluates to false Specifically CAG will walk its sub-tree & subscribe to activity state changes for all activities, this will stop at call boundaries CAG will add a subscription whenever an activity is added dynamically to its sub-tree CAG will subscribe to data changes for its enclosing scope and all parent scopes up to a schedule boundary, these subscriptions are determined by analysis of the enable and disable rules on all constrained activities in the CAG The engine will deliver batched notifications of data changes and the CAG will decide which rules to evaluate Note that data changes made by
a called schedule are posted when the call completes It is possible to identify scope variable dependencies even if those variables are accessed indirectly via code beside methods As such, it is possible to be very specific m determining which constraints should be reevaluated when a variable is changed This same mechanism will work for both declarative and code rules If a constrained activity has no enable rule, it is taken to always be true
If a constrained activity has no disable rule, it is taken to always be Performed>0 Thus, if no rules are specified on a constrained activity, it is executed immediately when the CAG executes, and it does not ever get re-executed Likewise, if only a custom enable rule is provided on a constrained activity, it will execute when that enable rule evaluates to true, and it will only execute that one time If constraint-based re-execution is desired, an appropriate custom disable rule must be provided, along with the appropriate enable rule
The following table illustrates the condition required to execute a constrained activity
EnableRule DisableRule Can activity execute*?
TRUE FALSE Yes
TRUE TRUE ~No
FALSE FALSE "No
FALSE TRUE ~No
Table A1 Constrained Activity Execution
If during the execution of an activity, the disable rule for that activity evaluates to true, the CAG cancels the execution of that activity This does not preclude re-execution of that activity As soon as the completion rule of the CAG evaluates to true, the CAG immediately cancels any currently executing child activities, and then itself completes All rules (enable, disable, completion) are evaluated whenever necessary based upon their data and state change dependencies
The CAG provides two operation modes Preview & Edit If the CAG designer is m Preview mode, the developer is only able to select the activity which appears the filmstnp The property browser exposes Enable and Disable rule options (detailed below) when a developer has selected any activity This allows a developer to set enable and disable rules for each activity with a CAG If the CAG designer is in Design mode, the developer is able to click on the activity in the preview window (called a Constrained) The property browser then displays the Enable and Disable rule options (like in preview mode) in addition to the properties normally exposed by the specific activity
The CAG designer provides a few additional context menu options Preview Activity
Given a selected activity, the CAG will switch from Design Mode to Preview Mode Edit Activity
Given a selected activity, the CAG will switch from Preview Mode to Design Mode View Previous Activity
Move to the activity immediately preceding the currently selected activity in the
filmstnp When you reach the first activity in the CAG filmstnp, this menu option is
disabled View Next Activity
Move to the activity immediately following the currently selected activity in the
filmstnp When you reach the last activity in the CAG filmstnp, this menu option is
disabled In one embodiment, each activity within a CAG is wrapped within a 'constrained activity ' This is then exposed to the developer via the filmstnp of the CAG If the CAG is in preview mode and a developer selects this activity and copies it, the only place where it may be pasted (and thus have the consequential context menu enabled) is within another CAG However, if the developer switches the CAG mode to "Design" and chooses the activity within the preview pane, copy/paste & drag-drop are enabled in a similar manner as with the remaining activities
Task
Purpose Model an external unit of work that is performed by one or more principals
Wraps a template activity that is either an InvokeSchedule or a custom activity
Metadata
• An execution mode, indicating either parallel or sequential execution
• The type of the underlying task implementation (called the template)
• A role indicating the assignees for the task
• An optional code-beside method that allows the developer to set task properties on a per-assignee basis
Execution
When the task is executed, first the role is resolved to a set of principals (assignees) If the role is empty then an exception is thrown The template activity is then cloned once for each assignee, and the optional code-beside method (example shown below) for initializing properties of the clones is then called if present Depending upon the execution mode, the individual assignee tasks are then executed in parallel or in sequence To achieve this, each assignee task (clone) is effectively wrapped in a constrained activity with appropriate enable and disable rules set Note that if the execution mode is sequential, the sequence is determined by the ordering of assignees that is returned by role resolution As with CAG (parent activity of task), if the completion rule becomes true, then the task completes and any outstanding clones are cancelled Otherwise, the task completes when all assignee tasks (clones) are complete
Event Driven
Purpose Wrap an activity whose execution is triggered by an "event" activity Execution
An EventDnven activity must have a parent that is either a Listen or an EventHandlers composite activity An EventDnven activity contains both an IEventActivity, and a second activity of any type The IEventActivity by definition blocks pending the occurrence of some event, such as the firing of a timer or the arrival of a message When the event occurs, the IEventActivity completes its execution, and then the second activity is executed Upon selection of an Event Driven (generally within an EventHandlers or Listen activity), two addition context menu operations appear Move Left (moves the selected EventDnven to its immediate left in the conditional) and Move Right (moves the selected EventDnven to its immediate right in the conditional)
Listen
Purpose Conditionally execute one of n child EventDnven activities
Execution
The Listen activity ensures that only the first of its child EventDnven activities to have its
IEventDnven child's event occur is allowed to execute All others are cancelled In
concept, Listen is similar to a Conditional, in that exactly one of n branches is executed,
where the selection of the branch is determined by the occurrence of an event rather than by
procedural business logic
Event Handlers
Purpose Wrap a set of EventDnven activities The EventHandlers activity simply holds a set of EventDnven activities, for use by the associated Scope An EventHandlers activity may only be associated with a Scope
Exception Handler
Purpose Wraps an activity with metadata that represents a catch block for a scope
Metadata
• An enum indicating the type of the catch block
o All - catches all exceptions o Type - catches an exception of a specified type
o Variable - catches an exception of a specified type, and makes the exception available for inspection in a local variable of the code-beside
• A property indicating the type of exception caught (used only if the enum is set to Type)
• A reference to a local variable where the exception will be deposited (used only if the enum is set to Variable)
Execution
ExceptionHandler activities may only be added to an ExceptionHandlers activity in one embodiment The Scope associated with the ExceptionHandlers activity utilizes the metadata on its set of ExceptionHandler activities to determine which one to execute when the Scope receives an exception When the ExceptionHandler activity is told by the Scope to execute, it simply executes the activity that it wraps Upon selection of an ExceptionHandlers, two addition context menu operations appear View Previous Activity, View Next Activity
Exception Handlers
Purpose Wrap an ordered set of ExceptionHandler activities The ExceptionHandlers activity simply holds a set of ExceptionHandler activities, for use by the associated Scope An ExceptionHandlers activity may only be associated with a Scope in one embodiment When two or more ExceptionHandler activities exist, "Move Left" and "Move Right" context menu options are enabled
Compensate
Purpose Compensate a completed child scope
Metadata
• The ID of the child scope to compensate
Execution
The Compensate activity may exist only withm a compensation handler or an exception handler for a scope Its purpose is to trigger the compensation handler of a completed child scope
Compensation Handler
Purpose Wrap a child activity that is defined as the compensation handler for a scope
Execution
Executes its child activity A CompensationHandler activity may only be associated with a
Scope
Scope
Purpose A scope is a transaction boundary, an exception handling boundary, a
compensation boundary, an event handling boundary, and, a boundary for message,
variable, correlation set, and channel declarations (1 e shared data state) A scope activity is
a grouping of activities that acts as a logical container Often the purpose of a scope is to
apply transactional semantics to the enclosed set of activities
Metadata
• The Type of the scope's code-beside class
• A Boolean indicating whether the scope is a synchronized scope
• Several properties related to transactional characteristics of the scope
o The type of the transaction none, atomic, or long-running o The isolation level (if the transaction is atomic)
■ Chaos The pending changes from more highly isolated transactions cannot be overwritten
■ ReadCommitted Shared locks are held while the data is being read to avoid dirty reads, but the data may be changed before the end of the transaction, resulting in non-repeatable reads or phantom data
■ ReadUncommitted A dirty read is possible, meaning that no shared locks are issued and no exclusive locks are honored
■ RepeatableRead Locks are placed on all data that is used in a query, preventing other users from updating the data Prevents non-repeatable reads but phantom rows are still possible
■ Senahzable A range lock is placed on the DataSet, preventing other users from updating or inserting rows into the dataset until the transaction is complete
■ Snapshot Reduces blocking by storing a version of data that one application may read while another is modifying the same data Indicates that from one transaction you cannot see changes made in other transactions, even if you requery
■ Unspecified A different isolation level than the one specified is being used, but the level cannot be determined
o The timeout, in seconds (if the transaction is atomic)
o Whether the transaction is capable of being retried (if the transaction is
atomic) o Whether the transaction is batchable (if the transaction is atomic) o A code-beside method that returns a DateTime indicating a timeout value (if
the transaction is long-running)
• A code-beside method that executes when the scope begins executing This is essentially equivalent to a Code activity as the first activity within the scope This method is guaranteed to complete before any event handlers for the scope may execute An exception here is treated just as an exception within a Code activity mside the scope
• A code-beside method that executes when the scope finishes executing This is almost equivalent to a Code activity as the last activity within the scope, this code will execute only after any instantiated event handlers finish their execution An exception here is treated just as an exception within a Code activity inside the scope
• An optional set of event handlers
• An optional ordered set of exception handlers (not valid for scopes that are atomic transactions)
• An optional compensation handler
Execution
Execution of the activities within a Scope is sequential, and thus the contained activities are explicitly ordered when the scope is constructed, as in a Sequence As with other composite types, scopes may be nested, subject to some restrictions If a developer is referencing a type not declared within the scope but for any property within that scope, the property will be full qualified with the outer calling schedule name within the property browser Under normal circumstances, a Scope activity simply executes its "main" child activity, as well as any of its event handlers that fire If an OnScopelmtiahzed code-beside method is specified, that method is executed just as if it were a Code activity as the first item inside the scope Event handlers execute concurrently with the "main" child activity of the Scope, and are considered optional but normal aspects of the Scope's execution As in the Listen activity, the first activity withm an event handler must be an IEventActivity Typically, this is either a receive activity or a Delay but may be any custom activity that implements the appropriate interface A specific event handler may execute more than one time for a given Scope, and, it is possible for these instances of an event handler to execute concurrently New instances are guaranteed to be created for each "event" that fires for each event handler When the "main" child activity of a Scope completes its execution, all currently executing event handler instances are allowed to finish their execution normally But, new instances of any event handlers are not subsequently created If an OnScopeCompleted code-beside method is specified, that method is executed after both the mam body of the scope is finished, and all outstanding event handlers are finished
Essentially, a scope's Onlmtiahzed and OnCompleted methods are solidly inside the scope The only "special treatment" they get is
• No event handler may start before the Onlmtiahzed method completes
• The OnCompleted method is not executed until all currently running event handlers complete (along with the main body of the Scope)
• Once the OnCompleted method starts, no event handlers may run anymore Exceptions that occur in an event handler are treated exactly the same way as
exceptions that occur in the "mam" child activity of the Scope If a Scope is marked as a synchronized Scope, then this guarantees safe concurrent access to shared data Synchronized scopes cannot be nested Synchronized scopes that access the same shared data (external to both) are guaranteed that the results of their read/write operations on that data would be no different than if the scopes were serially executed A Scope also acts as an exception handling boundary, meaning that the Scope's exception handlers are shared by all nested activities within the scope (including any event handlers) If an exception is
thrown by an executing activity within a non-atomic Scope, the scope cancels all other executing activities and event handler instances, and then handles the exception if it has an exception handler that is able to catch the exception Once the exception handler executes, the Scope completes but with an outcome of Failed If no exception handler is defined for a non-atomic scope for a particular exception type, or if an exception handler throws an exception, then a default handler is created (for all uncaught exceptions) that runs all installed compensation handlers (see below) for child scopes, in reverse order of the completion of those child scopes, and then rethrows the exception to its parent Scope
An atomic scope cannot have associated exception handlers If an exception occurs during the execution of an atomic scope, the transaction fails, as does the execution of that scope The scope will itself produce an exception that is propagated to the next outer enclosing scope, which does have the ability to handle that exception A Scope whose execution completes normally (meaning that no exception occurred), has its compensation handler "installed" This compensation handler may subsequently be called, via the Compensate activity, from within either an exception handler of the parent scope, or the compensation handler of the parent scope If no compensation hander is defined for a completed scope, a default one is installed that runs all installed compensation handlers for child scopes, m reverse order of the completion of those child scopes Given the above, compensation occurs only in the context of some exception handler If an exception occurs during the execution of a compensation handler, it is treated as an exception withm that exception handler
In addition to the standard context menu options, the Scope activity exposes the following additional menu options View Scope
This is the default view of a scope when added to the designer Selecting this option
takes the developer back to this view View Exceptions
Selecting this option changes the UI m-place to display the exceptions associated
with the Scope This is only enabled when Transaction Type is Long Running or
None Stated another way, this menu is not available when Transaction Type is
Atomic View Events
Selecting this option changes the UI m-place to display the Event handler associated
with the Scope
View Compensation
Selecting this option changes the UI m-place to display the Compensation defined with the Scope This is only enabled (when the Transaction type property is set to Long Running or Atomic)
Schedule
Purpose A Schedule is the only top-level activity that the orchestration engine will execute
Metadata (in addition to Scope metadata)
• The Namespace of the schedule type
• A CompilationType enum that indicates whether the schedule is a standalone application, or a library (meant to be invoked from other schedules)
• The representation of the entire schedule in XOML format
• Parameter declarations
Execution
Other than the need to consume In and Optional-In parameters and produce Out parameters,
a Schedule executes exactly the same as a Scope
Parameters
Part of a schedule's metadata is the set of parameters that participate in its execution
Composite Activities
The composite activity types that enable control flow are Sequence, Parallel, Constrained Activity Group, Conditional, While, Listen Additionally, Scope and Schedule are composite activity types that act as containers with implied sequencing of the activities within them
ID & Description Properties
Every activity provides an ID and Description property When dragging an activity from the toolbox to the design surface, this ID is generated automatically The Description property is a placeholder for a developer to type Typical usage scenarios would involve a developer providing a short description of what a specific branch of a condition might be used for Conceptually, think of this property as an equivalent to a // in the Visual Basic and C# code editors
Help Text
When selecting a property in the property browser, the developer is able to hit the Fl key and index to the online help for that property Each property for each activity will provide the relevant help text
Task Error List & Property Browser Integration
When an activity's properties are insufficiently configured, developers are presented with an icon containing an exclamation point They may then click on the icon and see a dropdown list of the configuration errors Selection of one of the errors will move the focus to the Properties Browser and highlight the property in error The icon will disappear when the activity's properties are complete The errant configurations may also be seen in the "Task List" Doubling clicking on an error message presented in the Task List takes the developer directly to the property in the property browser
ID Generation
The default identifier of any activity added to the designer is created based on the number of similar activities which already exist As activities are added and removed, the identifier is created by the open slot in the range As an example, the first Send activity added would have an identifier as ' 1' The second, '2' and so on However, if five Send activities exist, the developer removes number 3 (via delete or cut) and then later re-adds another Send (via copy/cut/paste or through the toolbox), the identifier should be '3'
Valid Names for IDs
Developers may provide any name for an ID that is valid in the project's language
(including valid escaped names)
Multiple Selection of Activities
Developers will often wish to select a group of activities and move them to another area of
the schedule This could be accomplished on an activity by activity level, however, it is
more likely that a developer will select multiple activities at a time and drag them to this
new area
If the activities are of the same type, the property browser will be enabled to allow a mass
configuration of common properties For example, if all the activities selected are
constrained activity groups, then the Completion Condition property will be available for the developer to configure
If the developer selects a variety of different types, then the property browser will only provide the ability to configure properties which the activities share (for example, ID and description) During multi selection, the selected activities will be adorned with blue indicators on the corner of the activities These indicators will be shown as blue dots The activity which has the keyboard focus will be adorned differently It will be a solid versus a hollow fill to indicate that it is the activity in focus
Handler & Variable Generation
Many activities expose properties which generate variables and or code handlers in the code beside All properties which perform either action are called out in the property browser integration for each activity Creation of a new variable or handler is performed when a developer specifies a new variable or handler name via the property browser Take as an example the message variable for a Send When specifying "ml" of type System String, the resulting code beside is
public OEMessage ml = new OEMessage(), By specifying another value for a property which creates a code beside variable or handler, a new variable or handler is created The existing variable/handler remains intact It is incumbent upon the developer to delete the generated variable (or respective handler) In the scenario where the developer renames an existing variable in the code beside, the activities referencing it will not be updated It is again incumbent upon the developer to update each activity which referenced the original variable with this new variable
Copy/Paste and drag-drag operations across schedules when applied to the handlers for specific activities do not apply to the handlers associated with them When applied to Scopes, generation of variables and code handlers behaves m a slightly different manner More specifically, the generated variables and code handlers will be placed within the definition of the Scope Class All private, protected, internal and public methods and variables are from the activity's scope may be set on the activity (as long as types and signatures match) All public and internal methods and variables are from the activity's enclosing scopes may now be legally set on the activity (as long as types and signatures match)
Consequently, while creating these variables and handlers from the menus or from the property browser, the rules are as follows
• If the variable or method is to be created in the activity's scope, it is created private
• If the variable or method is created in any the activity's enclosing scopes, it is created public
Context Menu
When right clicking on an activity, its associated designer will provide a developer with activity specific actions For example, right clicking on a scope, will provide you with "View Scope, View Exceptions, View Events" in addition to the standard "View Code", Cut/Copy/Paste parameters
Here is a list of possible actions you may take based on commonalities View Code
View the code associated with the selected activity If an activity is selected and a handler has been specified, selecting this option should take the developer to the specified handler Cut
Remove the selected activity from the designer and copy it to the clipboard Copy
Copy the selected activity to the clipboard Paste
Paste the last copied activity from the clipboard to the designer If no selection area is selected, the activity will be copied as the activity in the schedule Delete
Deletes the selected activity Properties
Populate and set focus to the Property Browser for the selected activity Generate Handlers
Generate the corresponding handlers for the selected activity Expand
Expand the designer to expose its constituent parts Collapse
Collapse the designer to hide its constituent parts
Hotlink/Hyperlink Property Browser Integration
Each activity provides context menu options as Hyperlinks in the Property Browser For all primitive activities, this includes "Generate Handlers" Each composite activity will provide "Expand/Collapse" and context menu options specific to the activity These are detailed on a per activity level Activity Commenting
The orchestration engine designer allows the user to create complex hierarchical schedules These schedules may be very complex and hard to debut The commenting functionality gives user an ability to comment out parts of the schedule so that the commented activities will not be executed at runtime This simplifies the debugging and allows the user to monitor execution of part of the schedule at a time Activities expose a Boolean property to allow its "pseudo" removal from the schedule This activity is still present in the schedule, however at runtime, its existence will be ignored and it will not be executed A developer is able to enable/disable commenting by setting a property exposed in the Property Browser and via the context menu
The commenting functionality has design time as well as runtime implications Users are able to programmatically comment an activity as well as use the user interface provided by the designer The designer allows users to comment the shapes by selecting shapes and using property browser to set the comment property to true and rubberbanding and multi selecting the activities and selecting comment menu option on the context menu In response to the comment, the designer renders an activity designer semi transparent It is possible for the user to select the activity designer and set the properties on it The Xoml continues to have the commented shape in it, the only difference is the comment property being set to true The design time validation skips the commented activities and behaves as though the activities do not exist At runtime, the authoring object model offers two collections, which return activities and executable activities The runtime acts on executable activities
APPENDIX B
Activity Designers
The IActivityDesigner interface is implemented by all the activity designers which need to participate in the workflow This is a protocol by which the designers talk with other designers and workflow view The workflow view looks for the IActivityDesigner interface in order to render, layout or forward events to the designer Supporting IActivityDesigner interface enables all the designers to act like windows control even though designers are not really derived from windows control This interface also enables the workflow view and other designer infrastructure like adornment service, menucommand service to exchange information with the designers The designers derived from IActivityDesigner interface cannot have a hierarchy, in order to have a hierarchy the designers need to implement ICompositeActivityDesigner interface Following is the definition of IActivityDesigner with the details about properties and methods

(Table Removed)

Table B2 Properties and Methods of ICompositeActivityDesigner Simple Designers
ActivityDesigner class represents the simplest implementation of a designer All the designers associated with activities in workflow are derived from ActivityDesigner ActivityDesigner class inherits from IActivityDesigner interface and provides default implementation for the interface The workflow view talks with the designer using the IActivityDesigner interface ActivityDesigner class is typically inherited by the designers which need a very lightweight implementation for the drawing of designers These designers do not have any children or hierarchy The features offered by the activity designer include basic layouting logic, rendering support (e g , by drawing icons, description, border, interior and background), rendering the help text, returning default glyphs needed by all the designers, showing context menu through DesignerVerbs, filtering of design time specific properties, default event generation, default hittesting, triggering validation, showing tooltip, and participation in keyboard navigation
public abstract class ActivityDesigner ComponentDesigner, IActivityDesigner System Object System ComponentModel Design ComponentDesigner System Workflow ComponentModel Design ActivityDesigner
System Workflow ComponentModel Design CompositeActivityDesigner System Workflow ComponentModel Design CodeDesigner System Workflow ComponentModel Design CompensateDesigner System Workflow ComponentModel Design DelayDesigner System Workflow ComponentModel Design FaultDesigner System Workflow ComponentModel Design CompositeScheduleDesigner System Workflow ComponentModel Design InvokeWebServiceDesigner System Workflow ComponentModel Design BaseReceiveDesigner
System Workflow ComponentModel Design BaseSendDesigner System Workflow ComponentModel Design GenericTaskDesigner System Workflow ComponentModel Design STSTaskDesigner
Composite Designers
CompositeActivityDesigner are the designers which have hierarchy (e g , they have children underneath) The CompositeActivityDesigner are responsible for managing all the aspects of itself as well as its children It is also responsible for interacting with its children for forwarding the events Whenever there is a request to modify the activity designer collection contained by the CompositeActivityDesigner, it is passed a context (ContextBase) which specifies the place from which the activity needs to be removed ContextBase may be specialized by each CompositeActivityDesigner derived class to specify context specific to them Example of this is SequentialActivityDesigner which specializes ContextBase by deriving a class called ConnectorContext from it The CompositeActivityDesigner class derives from the ICompositeActivityDesigner interface and provides default implementation for it The features provided by the CompositeActivityDesigner include expanding/collapsing of the designers, drag and drop indicators, lay outing of self and children, drawing of self and children, hittesting of the children, and inserting removing activities from hierarchy
public abstract class CompositeActivityDesigner ActivityDesigner,
ICompositeActivityDesigner
System Object System ComponentModel Design ComponentDesigner System Workflow ComponentModel Design ActivityDesigner System Workflow ComponentModel Design CompositeActivityDesigner System Workflow ComponentModel Design SequentialActivityDesigner System Workflow ComponentModel Design ParallelActivityDesigner System Workflow ComponentModel Design ConstrainedActivityDesigner
CompositeActivityDesigner is an abstract class and cannot be instantiated as it cannot exists on its own Sequential, Parallel and CA designers are all specializations of this class
SequentialActivityDesigner
SequentialActivityDesigner class represents all the designer which has children underneath and all the children are ordered sequentially The children are connected by links called connectors which are also used to modify the sequence of children The SequentialActivityDesigner class is a specialization of CompositeActivityDesigner and provides following set of features connector start and end bitmap drawing, layouting of all the children sequentially and updating all the connectors linking them, drawing of connectors between the children, highlighting drop areas when drag drop takes place, hittesting the connectors, sequential keyboard navigation using up and down arrows, and returning glyphs for connectors
internal abstract class SequentialActivityDesigner CompositeActivityDesigner
System Object
System ComponentModel Design ComponentDesigner
System Workflow ComponentModel Design ActivityDesigner
System Workflow ComponentModel Design CompositeActivityDesigner
System Workflow ComponentModel Design SequentialActivityDesigner
System Workflow Design ActivityPreviewDesigner
System Workflow Design CompensationHandlerDesigner
System Workflow Design ConditionedDesigner
System Workflow Design EventHandlerDesigner
System Workflow Design ExceptionHandlerDesigner
System Workflow Design ScopeDesigner
System Workflow Design SequenceDesigner
System Workflow Design WhileDesigner
All the above designers are specializations of SequentialActivityDesigner, they all mainly differ in drawing All of these designers have a special way of representing themselves on in the workflow but they all work off a common functionality provided by SequentialActivityDesigner
ParallelActivitvDesigner
ParallelActivityDesigner is another specialization of CompositeActivityDesigner which contains multiple SequentialActivityDesigners Each of these SequentialActivityDesigners is a branch in parallel designer The parallel designer offers the following specialized
features lay outing of multiple sequential designers, drag and drop indicators for adding additional branches, keyboard navigation for traversing between parallel branches by using left and right arrow keys, and drawing connectors to link the multiple parallel branches internal abstract class ParallelActivityDesigner CompositeActivityDesignerSystem Object
System ComponentModel Design ComponentDesigner
System Workflow ComponentModel Design ActivityDesigner
System Workflow ComponentModel Design CompositeActivityDesigner
System Workflow ComponentModel Design ParallelActivityDesigner
System Workflow ConditionalDesigner
System Workflow ListenDesigner
System Workflow ParallelDesigner
Conditional, Listen and Parallel designers are specialization of ParallelActivityDesigner with additional drawing logic associated with them
ActivitvPreviewDesigner
ActivityPreviewDesigner is sequential designer but has an ability to show collection of multiple designers in the form of collection bag ActivityPreviewDesigner uses the metaphor of filmstnp to display this collection When a particular designer is selected it's representation is shown in the preview window which the activity preview designer hosts The ActivityPreviewDesigner has two modes edit mode and preview mode In the preview mode, users cannot modify the designer which is selected This mode enables the user to see the entire representation of the designer without needing to scroll Edit mode allows the designer to be modified Features offered by the ActivityPreviewDesigner include preview strip to show the collection of activities, preview of the currently selected activity, and ability to edit selected designer
internal abstract class ActivityPreviewDesigner SequentialActivityDesigner
System Object System ComponentModel Design ComponentDesigner System Workflow ComponentModel Design ActivityDesigner System Workflow ComponentModel Design CompositeActivityDesigner System Workflow ComponentModel Design SequentialActivityDesigner
System Workflow Design ActmtyPreviewDesigner
System Workflow Design GenencCollectionDesigner
System Workflow Design CAGDesigner
Scope & Service Designer
Scope and Service designers are special designers Each of these may have exceptions, events and compensation associated with them Scope and Schedule also have a class associated with them in the user code file and user has ability to scope variables in these classes Scope and Service designers are illustrated differently than other designers and show a watermark and highlight them by drawing a drop shadow
Scope and Service designers have ability of changing the views so that a user may flip the views to reveal exception, events and compensation associated with them When the user hovers on the Service or Scope icon, a drop down palette appears which allows the user to pick one of the exception, event or compensation views The designer view is then flipped and the activities contained in the selected view are shown User may only view activities belonging to any one of the view at any point of time The flipping of views is achieved by filtering the child activities contained in the Scope or Schedule Scope and Schedule may have at most one of ExceptionHandlers, EventHandlers and Compensation as its children Based on the view which user is looking at, the designer filters out these children to only show the child activities which may appear in the chosen view, thus achieving effect of supporting multiple views Schedule designer is usually set as the root designer in the workflow view
internal class ScopeDesigner SequentialActivityDesigner
internal class ServiceDesigner ScopeDesigner
System Object
System ComponentModel Design ComponentDesigner
System Workflow ComponentModel Design ActivityDesigner
System Workflow ComponentModel Design CompositeActivityDesigner
System Workflow ComponentModel Design SequentialActivityDesigner
System Workflow Design ScopeDesigner
System Workflow Design ServiceDesigner
ServiceRootDesigner
ServiceRootDesigner is associated with the Root component contained by Designer Host It is responsible for creating the workflow view which is then hosted in designer window pane ServiceRootDesigner also supports IToolBoxUser interface which gives the ability to add toolbox items in the workflow by double clicking on the toolbox items
Design-time Descriptors
Each activity in the authoring object model has meta-data that describes its behavior during design-time This includes associating the activities (designers) as well as property grid behavior (naming, description, filtering, property editors, etc ) Type\Property\Event design time behavior is described using a zero or more of the following attributes
- SRCategoryAttribute - orchestration engine attribute Provides localized category name
- SRDescnpUonAtttibute - orchestration engine attribute Provides localized description
- EditorAttnbute - provides a UITypeEditor
- TypeConverter - provides filtering, value list, and conversion between types
- BrowsableAtmbute - show\hides members during design time
SRCategory and SRDescnption are merely mapping between a resource name and a string Most editors (UITypeEditor) are managers for handling dialogs (like the CorrelationSetsDialog) or dropdown lists The PropertyDescnptor handles the property in design time and is handed the property either by a default TypeConverter, a custom TypeConverter (that is declared as attribute as above) or a TypeDescnptor
UI Type Editors Provide editors to various properties in the orchestration engine Component model The Property browser use them to display ellipsis or drop down and to launch the editors
Type Converters
The type converter provides methods to convert the object to/from other types, provides a PropertyDescnptor list that represents the object properties in design time and might provide values to be used in a property grid's property's dropdown
Followed are some of the TypeConverters implemented in the orchestration engine Component model
- DeclTypeConverter
Base class to all activity's Type converters Implements CanConvertFrom(), CanConvertTo(), ConvertFrom(), ConvertTo() that convert activity objects to/from strings (To display the name of the activity in the property grid, and allow name editing to create the activity) Also, GetSite () provides access to the services
- HandlerDeclTypeConverter
Type converter for events Derives from DeclTypeConverter Implements GetStandardValues() that uses IEventBindingService to display compatible handlers
- VanableDeclTypeConverter
Type converter for variables (messages, channel, correlations etc') Derives from DeclTypeConverter Implements GetStandardValues() that uses IFieldBindmgService to display compatible variable fields In addition, the Type converter filters out the "Name" property and set a special propertyDescnptor for the type property that manifest as generic type
Property Descriptors
Property descriptor provides design time services to activity objects It provides name, description, category, type converter information as well as additional functionality when getting\setting the property value By default, the TypeConverter will provide the PropertyDescnptors to all properties The TypeConverter, however, may remove, add, or wrap them to provide a different design-time behavior of the type
Followed are some of the PropertyDescnptors implemented in the authoring object model
- DynamicPropertyDescnptor
Base class to all property descriptors in the authoring object model Implements a wrapper around the default property descriptor and delegates all the methods to it In addition, provides access to the object site, either directly from the object (if it is component) or via the IReferenceService
- VanableDeclPropertyDescriptor
Property descriptor for all variables (message, channel, correlation, etc ) Overloads SetValue() to provide code beside field as follows -Get the variable to set and its site
-Get the site of the containing scope
-Get the IFieldBindingService of the containing scope Note that each scope has its own IFieldBindingService with its own set of fields -Validate the field name with the service -Open a designer transaction -Save the value
-Call IFieldBindingService CreateField() to add the field to the code beside file -Commit the transaction - HandlerDeclPropertyDescnptor
Property descriptor for all Handlers Overloads SetValue() to provide code beside field as follows
-Get the HandlerDeclaration object to set and its site -Get the IEventBindingService -Open a designer transaction -Create a LocalEventDescnptor -Get the PropertyDescnptor for the event (using eventBmdmgService GetEventPropertyO) and set the HandlerDeclaration on it -Set the "Name" property of the HandlerDeclaration object -Commit the transaction
- ArrayElementPropertyDescriptor
Property descriptor that represents an item in a collection Since collection items -for example, Correlation Sets - do not have property descriptor (they are not properties) the ArrayElementPropertyDescriptor fakes a descriptor as if they were properties, thus allows to display them inside a property browser This property descriptor was designed to be wrapped by any of the property descriptors described above
- LocalEventDescnptor
EventDescnptor for represent Handler Declarations Handlers in the authoring object model are not real events, but properties, so we introduce our own EventDescnptors for the IEventBindingService to be used
Using ICustomTypeDescriptor
ICustomTypeDescnptor is an alternate way for setting descriptors for a component The
component itself implements the interface and provides the descriptors, as type converter,
defaults, etc GenencActivity, InvokeWebServiceActivity and InvokeSchedule implement this interface
Using IExtenderProvider
This is yet another technique for introducing design time properties to a component The extension class RulePropertyProviderExtender provides rule properties to the ServiceDesigner Properties are added by decorating the extender class via ProvidePropertyAttnbute, implementing getter and setter for the attribute, and adding the extender class to a IExtenderProviderService class (in our case, implemented by RulePropertyProviderExtender) that is accessible through the site of the component (Schedule Site)
Extensibility Support
The System Workflow ComponentModel Design namespace provides various reusable classes for user to use in creating their own activity designers and plugging them into the orchestration engine designer Following is the list of classes which user may use
- ActivityDesigner ActivityDesigner gives the user ability to add simple activities which do not have hierarchy of other activities under it The user needs to inherit from this designer and may customize the bitmap, description and drawing
- SequentialActivityDesigner SequentialActivityDesigner allows the user to write a designer which may contain multiple activities in it All of these activities are arranged sequentially and are linked using connector lines User may derive from this class and provide custom coloring, description, icon etc
- ParallelActivityDesigner ParallelActivityDesigner enables user to write activity designer which may have multiple composite activities in it, arranged in parallel fashion This class also enables the user to customize description, icon, colors, etc This class is extensible thru inheritance
- OrchestrationEngineToolboxItem OrchestrationEngineToolboxItem allows the user to create a custom toolbox item This class gives user an ability to control serialization The class provides hooks using which the user may popup custom UI when an activity is added in the designer The user may reuse this class through inheritance The user needs to provide the toolbox item by using the ToolBoxItem attribute
- TypeBrowserEditor The TypeBrowserEditor allows the user to browse the types available in the designer This class is used by associating it with a property which is of
type System Type The user uses UITypeEditor attribute to associate this class with a property
- TypeConverter classes the orchestration engine component model provides various type converters which allow the user to define their own type converters All the type converters may be used by extending them through inheritance
- DesignerGlyph Designer Glyph class may be used by the user to draw custom glyphs on top of the designers The may want to display certain visual glyphs which need drawing at the top most Z order The DesignerGlyph class may be used to draw such glyphs This class may be used by extending it through inheritance
- DesignerAction User may associate DesignerActions with DesignerGlyphs The actions are shown when the user clicks on the DesignerGlyphs Custom designer actions may be created by inheriting from DesignerAction class
APPENDIX C
Semantic Validation of Activities
These exemplary validation checks are common to multiple activities developed by the
orchestration engine
All Activities
- The ID property of an activity must be a valid identifier in the language of the project (C# or VB)
- The ID of a non-Scope activity must be unique within the containing Scope The ID of a Scope activity must be unique across all Scopes
- Any properties that are variables must be set to a variable that is visible - e g , it is defined in the Scope of the activity or in a containing Scope and must be public
Code-Beside Handlers
- The ID property of an activity must be a valid identifier in the language of the project (C# or VB)
- The Handler must exist in the code-beside scope class of the activity containing the Handler and must have a matching method signature
Messages
- The parametric type T of OEMessage must be senahzable
Correlations
- The parametric type T of OECorrelation must implement IComparable
Rules
- The Handler of the Rule must pass handler validations The signature of the handler is
defined by the type of Rule
Activity-Specific Validation Checks
These exemplary validation checks are specific to an activity type
Code
- The UserCodeHandler property must be specified and must have signature void
MethodO
Compensate
- A Compensate activity may appear only inside an ExceptionHandler activity or a Compensation activity of a Scope with TransactionType not None
- If CompensateScope is True, then the Scope property must be set to a Scope activity which is either an immediate child of the Scope from where the Compensate is emanating or itself
- If CompensateScope is False, then the Invoke property must be set to a CompositeSchedule activity which is an immediate child of the Scope from where the Compensate is emanating
Conditional
- A Conditional activity must have at least one child
- Only ConditionalBranch activities are allowed as children
ConditionalBranch
- The parent activity must be Conditional
- Unless the ConditionalBranch is the last child of its parent, the Rule property must be specified
ConstrainedActivity Group
- The CompletionRule property must be set to a valid Rule
- Only Constrained activities are allowed as children
Constrained
- The parent activity must be ConstrainedActivityGroup
- A Constrained must have exactly one child
- The DisableRule and EnableRules, if specified, must be valid
Delay
- The TimeoutProvider property must be set to a valid Handler
EventHandlers
- The parent must be a Scope activity
- Only EventDnven activities are allowed as children
- If the first child of any child EventDnven activity is a Receive with Activation set to True, then all child EventHandlers must have as first child a Receive with Activation set to True
- Only one child EventDnven activity may have a Delay activity as its first child
EventDnven
- The parent must be a Listen activity or an EventHandlers activity
- The first child must be either a Delay or a Receive activity
- At least one child activity must be present
Fault
- The ExeceptionProvider property must be set to a valid Handler with the signature System Exception Method()
- A Fault activity cannot be nested inside a Scope activity with TransactionType set to Atomic
InvokeSchedule
- The type of the mvokee must derive from InvokeSchedule and must have the default constructor
- Any public property of the mvokee that has the InAttribute, OutAttnbute or OptionalAttribute may be assigned to with visible variables of assignable types
- If the ExecutionMethod property is set to Exec, properties with the OutAttnbute but not the InAttribute cannot be assigned to
- If the ExecutionMethod property is set to Exec, the variables must be senahzable
- A Channel or a Correlation cannot be assigned to a property with the OutAttnbute
- Recursive invokes are not allowed
Invoke WebService
- The ProxyClassName property must be set to a valid proxy class
- The MethodName property must be set to a web method in the proxy class
- All parameters to the web method must be specified and visible and their types must
be assignable Further, for any out/ref parameters and the return value, the parameters
specified must not be read only
Listen
- Only EventDnven activities are allowed as children
- At least two children must be present
- If the first child of any child EventDnven activity is a Receive with Activation set to True, then all child EventDnven activities must have as first child a Receive with Activation set to True, or a Delay activity
- Only one child EventDnven activity may have a Delay activity as its first child
Parallel
- Only Sequence activities are allowed as children
- At least two children must be present
- If the first child of any child Sequence activity is a Receive with Activation set to True, then all child Sequence activities must have as first child a Receive with Activation set to True
Receive
- The Message property must be set and valid
- If the HasTypedChannel property is True, the TypedChannel property must be set and valid - a visible variable of type OEInboundChannel where T is an interface
- If the HasTypedChannel property is True, the Operation of the TypedChannel must be a method from the interface which has a signature void Method(Type parameter)
- If the HasTypedChannel property is True, the Type of the Message must be assignable from the Type of the Operation's parameter
- If the HasTypedChannel property is False, the UntypedChannel property must be set and valid - a visible variable of type InboundChannel
- If the Activation property is True, the Receive must be the first executable statement in the Schedule and may only have Sequence, Parallel, EventDnven, Listen, Scope or Schedule activities as ancestors
- If the Activation property is True, the Schedule must not have the CompileAs property set to Activity
- If the Activation property is True, the Receive must not be nested inside a Compensation or an ExceptionHandler or a While activity
- If the Activation property is False, the Receive must follow at least one Correlation
- A Correlation may be specified at most once and cannot be initialized and followed at the same time
- The OnAfterReceive handler if set must have a signature void Method()
ReceiveRequest
- The Operation of the TypedChannel property (if it needs to be set) must have the
signature ReturnType Method(Type parameter)
ReceiveResponse
- The Operation of the TypedChannel property (if it needs to be set) must have the signature ReturnType Method(Type parameter)
- The ReturnType of the Operation must be assignable from the Type of the Message
- The SendRequest property must be the qualified name of a valid SendRequest activity
- The SendRequest activity must occur before the ReceiveResponse
- The SendRequest and the ReceiveResponse activities must not be nested inside the same Atomic Scope
- The ReceiveResponseActivity cannot follow a Correlation
Send
- The Message property must be set and valid
- If the HasTypedChannel property is True, the TypedChannel property must be set and valid - a visible variable of type OEOutboundChannel where T is an interface
- If the HasTypedChannel property is True, the Operation of the TypedChannel must be a method from the interface which has a signature void Method(Type parameter)
- If the HasTypedChannel property is True, the Type of the Operation's parameter must be assignable from the Type of the Message
- If the HasTypedChannel property is False, the UntypedChannel property must be set and valid - a visible variable of type OutboundChannel
- A Correlation may be specified at most once and cannot be initialized and followed at the same time
- The OnBeforeSend handler if set must have a signature void MethodQ
SendRequest
- The Operation of the TypedChannel property (if it needs to be set) must have the
signature ReturnType Method(Type parameter)
SendResponse
- The Operation of the TypedChannel property (if it needs to be set) must have the signature ReturnType Method(Type parameter)
- The ReturnType of the Operation must be assignable from the Type of the Message
- The ReceiveRequest property must be the qualified name of a valid ReceiveRequest activity
- The ReceiveRequest activity must occur before the SendResponse
- The SendResponseActivity cannot follow a Correlation
Scope
- A Scope activity with the Synchronized set to True cannot be nested inside another Scope activity with Synchronized set to True
- A Scope activity with TransactionType Atomic cannot be nested within an ExceptionHandler activity
- A Scope activity with TransactionType Atomic or LongRunning must be nested within a Scope activity with TransactionType as LongRunning (unless the Scope is the Schedule)
- If the TransactionType is Atomic, the Synchronized property must be True
- If the TransactionType is Long Running, the TimeoutProvider handler must be set with a signature System DateTime Method()
Schedule
- The code beside class must have exactly one constructor
Sequence No validations
Suspend
- A Suspend activity cannot be nested inside a Scope with TransactionType set to Atomic
- The ErrorString property must be a valid string
Terminate
- The ErrorString property must be a valid string
While
- The ConditionalRule property must be a valid Rule
Correlation Set and Convoy Validation Checks
These exemplary validation checks are specific to correlation sets and convoy scenarios
- A Correlation must be initialized before it may be followed
- A Correlation may be initialized at most once with some exceptions
- A Send that initializes a correlation and a Receive that follows it reside in the same Atomic Scope
- Detection of sequential convoys
- Detection and validation of parallel convoys
o All Receive activities in a parallel convoy must initialize the same set of
Correlations o All non-activation Receive activities in a parallel convoy must follow the
same set of Correlations o An activation Receive in a Parallel must initialize a Correlation
If an activation Receive is the first executable non-composite activity (e g , ignoring Scopes, Parallels, Listens, etc ) in the workflow and its ancestor is a Parallel or a Listen, then all the branches of the Parallel or Listen must have an activation receive as its first executable activity
APPENDIX D
Exemplary Namespace APIs
A System Workflow ComponentModel namespace contains the implementation of standard Workflow Activities An Activity object model provides APIs to author an orchestration program In addition, every object in the declaration object model has inheritance which makes it possible to associate design time behavior with the component Following is an example of representing an orchestration program which receives a message and sends it using the declaration object model
service Service 1
{
message msgl, port portl, port port2, receive(portl, msgl), send(port2, msgl),
} The corresponding Authoring APIs to construct such a service include // declare a service with name "Service 1" Scheduel schedule = new Schedule ("Servicel"), schedule TransactionType = TransactionType Atomic,
// declare receive with name "receive 1" and which uses port "portl" and message "msgl"
Receive receive 1 = new Receive ("receive 1"), receivel Port = "portl", receive 1 Message = "msgl", schedule AddActivity(receivel),
// declare send with name "sendl" and which uses port "port2" and message "msgl" Send sendl = new Send ("sendl"), sendl Port = "port2", sendl Message = "msgl", schedule AddActivity(sendl), // give external user code to the service declaration

serviceDeclaration ExternalUserCode = "",
The following table briefly describes the description and uses of this namespace

(Table Removed)
Table B1 System Workflow Component Model Namespace Model The Workflow component model is a hierarchical declaration object model The root of the object model is Schedule This object model is used by tools writers as well as run-time execution Every activity in the component model is represented by IActivity interface IActivity interface inherits from IComponent IComponent has a Site property which allows the activity to communicate at design time This object model may be extended by third party activity writers Activities may be categorized as following
1) Primitive Activity a primitive activity has no child activities and it includes a flat list of properties
2) Composite Activity a composite activity inherits from a primitive activity and keeps a list of child activities
In addition to Primitive and Composite activity categorization above, Scope and Schedule activities are treated differently Scope and Schedule have a corresponding User Code class associated with them Along with all the Activities, this namespace also provides following features Serialization and Deserialization from/to xoml files, Compilation of Schedule activity, and Validation implementation on each Activity
The IActivity interface inherits from IComponent
public interface IActivity IComponent
{
//This is the unique identifier of an activity with in its parent scope
//Across scopes this id may have duplicate values To identify activities across
scopes a scope //qualified name must be used Also for Scope and Schedule this
property tells the name of//the user code class they work with
string ID {get, set,}
//This property returns the qualified ID of the activity Qualified ID of the activity is
//ParentScope ID combined with a " " And the activity ID
string QualifiedID {get,}
//This a get set property used to hold description about an activity in the process
String Description { get, set,}
//This is a get set property to comment or uncomment an activity If an activity is
commented //then it does not participate in the execution and validation checks
bool Commented { get, set,}
//This is a get property which tells if an activity is instantiated for RuntimeMode
Usually when //activity graph is instantiated for run-time mode activities makes all
of their properties read-//only so that user will not be able to change them
bool IsRuntimeMode { get,}
//This method returns the state of an activity at run-time time Because the multiple
//orchestration instances share the same activity tree, this method takes the pointer to
the //instance of the orchestration, based on that the IActivityState interface will be
returned for //that particular activity and the instance The IActivityState interface
provides a way to get //the Status and Outcome properties
IActivityState GetState(object scopeBoundObject),
//The purpose of this property is to allow programmatically associate some custom
data with //the activity This is to be used for programming against activity DOM
IDictionary UserData {get, }
//This property tells the parent activity of this activity
ICompositeActivity Parent { get, set, }
//This property tells the parent scope of the activity This property walks
//through all the parents, till you get a scope Also please note that the ParentScope
of an //scope returns the parent scope only
IScope ParentScope { get, }
//This function is used to validate the activity It is passed in a context in the form of
//IServiceProvider, from which the activity writers may get different services to
validate the //contents of activity Currently this function is called from Xoml
compiler and as well as //designer Two services include 1) ITypeProvider 2)
//IEnvironmentService
IVahdationError[] Vahdate(IServiceProvider context),
} Following is the definition of IVahdationError This error is returned on calling Validate on the activity
public interface IVahdationError
{
//Error text returns the description of error
string ErrorText { get, }
//The purpose of this property is to allow programmatically associate some custom
data with //the error For an example the 'typeof(strmg)' key in this property should
keep the name of//the property
IDictionary UserData { get, }
} Every composite activity inherits from ICompositeActivity Composite Activity has
additional properties "Activities" and ExecutableActivities in compare to Primitive activity Following is the interface definition of ICompositeActivity public interface ICompositeActivity IActivity
{
// This property is used to get all the child activities Please note that // this returs IltemList of activities instead of IList of activities IltemList // is an interface defined in activity DOM, which has an extra event // to notify when an activity is added ot removed from the list IActivityCollection Activities { get,} // Execuable activities returns the collection of non-commented activities
This
// property only returns a readonly collection of activities If the user wants to
change,
// add or delete activities, then "Activities" collection should be used IList ExecutableActivities { get, }
} IActivityCollection inherits from IList, it has one additional event about modifications to
the list and couple of more methods related to dynamic update of collection in runtime mode
public interface IActivityCollection IList
{
//Only event which is fired when some item is added, removed or replaced from this
list
event ItemListChangeHandler ListChanged,
//Indexer property to get to an activity based on the ID property of the activity
IActivity this[stnng key] { get,}
//Method to dynamically change the activities collection at run-time These methods
takes the //pointer to an ScopeBoundObject (the instance to which the modifications
are getting applied)
//To Add activity
void Add(object scope, IActivity activity),
//To Add activity range
void AddRange(object scope, ICollection activities),
//To remove an activity
void Remove(object scope, IActivity activity),
//To replace an activity
void Replace(object scope, IActivity replaceThis, IActivity withThis),
}
Run-Time Value Provider
The value of the activity properties are constants or pointers to a variable or method in the code-beside file For an example, Message property on Send activity points to a member variable in the code beside file, also the ErrorStnng property of Terminate activity might want to keep the actual string in the literal form or it might want to point to an variable in the code beside file From the run-time perspective, it only cares only about getting a value for the property, this could be either a literal from which the value is retrieved or a variable in the code beside file
public abstract class RuntimeValueProvider
{
// This property get the type of the value which this object will return
Type RuntimeType { get, }
// This method is used to retrieve the value of a property at run-time object GetValue(object scopeBoundObject),
} In one embodiment, there are two different kinds of value providers, 1) Literal Declaration 2) Member Declaration
MemberDeclaration
These objects represent a variable or method name in user code file of a particular run-time type For an example, the Message property on the Send points to a variable in user code beside file, which must be of type "System Workflow Runtime OEMessage" Such a property is of type 'string', and the value of it is the name of the variable Non-Activity classes have some meta data associated with them in addition to the string value For example, these may tell what run-time type these variable should refer to etc
public class MemberDeclaration
{
// The name property points to member variable or method in the code beside file
The name // may be Scope qualified
string Name { get, set,}
// This property stores the type of the variable or handler declaration in the code
beside file Type RuntimeType {get, set,}
// This property only gets a value at run-time, it will only get value when the object
of this class is instantiated for run-time mode
Scope Scope { get, }
// This property tells that if the object is been instantiated for run-time uses
bool IsRuntimeMode {get,}
// The validate method validates this object and returns collection of validation
errors It passed in the activity of which this object is part of and the name of the
parent property
IVahdationErrorf] Vahdate(IServiceProvider serviceProvider, IActivity activity,
string parentPropName), }
There are two mam inheritance branches from MemberDeclaration 1) VanableDeclaration 2) HandlerDeclaration VanableDeclaration is used to refer to a variable in the user code beside file, and HandlerDeclaration is used to refer to a method in the user code beside file VanableDeclWithOneArg inherits from vanableDecl and is used to refer to a variable in the user code beside file, whose runtime type is generic type with one argument
Also there is a lot of design time functionality associated with these declaration classes For an example, using VanableDeclaration as a property type for your activity automatically gives a combo box in the property browser window to list all the variables in the code beside file of a particular runtime type Also these classes have functions to do semantic checks For an example, HandlerDeclaration checks if the method name is valid, if the method exists in the user code file, and if the signature of the method matches that identified by the runtime type property
Variable Declaration
VanableDeclaration inherits from MemberDeclaration and stores the name of the variable in the code beside file It has three additional methods at run-time mode
public class VanableDeclaration MemberDeclaration
{
// The Fieldlnfo object which will be pointing to the vanable in the code beside file
at run-time
public Fieldlnfo Fieldlnfo { get,}
// Method to get the value of the variable at run-time for a particular instance of the
schedule
public object GetRuntimeValue(object scopeObj),
// Method to set the value of the variable at run-time for a particular instance of the
schedule
public void SetRuntimeValue(object scopeObj, object value),
} TypedVanableDeclaration inherits from VanableDeclaration and makes the run-time type property read-only
Handler Declaration
HandlerDeclaration inherits from MemberDeclaration and points to a method name in the code beside file It has one additional method at run-time which returns the delegate object which will be pointing to method in the code beside class
TypedHandlerDeclaration inherits from HandlerDeclaration and it makes the runtime type property to be read-only
Literal Declaration
The LiteralDeclaration object contains a literal value instead of pointing to a variable in the code beside file Following is the definition of the class
public class LiteralDeclaration RuntimeValueProvider
{
// This property is used to get or set the literal value
string LiteralValue { get, set,}
}
Rule Declaration
Rules are used in business processes to dynamically change the behavior of an orchestration The Workflow component model defines a way to plug in arbitrary rules technology To implement a custom rules technology, one has to define a class which inherits from RuleDeclaration It has abstract methods to validate the rule and to inform inherited classes about the run-time initialize mode The custom rule technology provider inherits from the RuleDeclaration class and overrides these methods Also, it provides additional properties which are used to define a rule definition
Currently the workflow component model has two RuleDeclarations classes, one is the Code based rule declaration, which has a Boolean handler method associated therewith to evaluate the rule and return a true or false value Another technology is BRE based rule declaration, which provides an object model to define the rule The run-time counterpart of the rule declarations classes is the RuleEvaluator Workflow engine looks for RuleEvaluator attribute on the RuleDeclaration class This attributes tells the name of the Type which implements the IRuleEvaluator interface The IRuleEvaulator interface has only one method Evaluate() which returns a Boolean value
Runtime Mode
The same activity graph which is used to author an orchestration program at design time is also instantiated at run-time At run-time the workflow engine calls the root object of the activity graph to execute itself, which in turn calls its children activities to execute themselves and so on the children activities which are composite activities ask their children activities to execute themselves When the activity graph is instantiated for run-time uses, then the activities do not allow changing their properties
An activity may know about the run-time initialization by overriding OnRuntimelmtiahzedO method, which is an protected method defined in the Activity class Activities may do custom run-time specific initialization in this method Usually on runtime instantiation of activities, they resolve their stnngified information into actual run-time type information For an example a Invoke Web Service activity keeps the name of the proxy class in the string form at design time, when the invoke web service is instantiated for run-time it resolves the proxy class name into the actual System Type object
Workflow engine only keeps one activity graph for multiple instances of the running orchestrations The GetState(object scopeBoundObject) method on the activity returns IActivity State for a particular instance of the orchestration Using IActivity State interface one may get the Status and Outcome property of an activity
public interface IActivityState
{
//To get the status of an activity At run-time execution mode the activity goes
through //multiple state transitions ex Enabled, Executed, Completed, Closed,
Cancelled The status //property tells the exact current state of the activity
Status Status { get, }
//Workflow engine keeps the Outcome of an activity's execution If the activity
//execution gets cancelled then the Outcome would be cancelled, if the activity
//execution throws an exception then the Outcome would be Failed other wise if
activity //got completed and closed then the Outcome would be Succeeded
Outcome Outcome { get, }
}
Parallel to run-time instantiation of the activities the non-activities declarations are also instantiated for run-time mode For an example a VanableDeclaration whose name is "art" and run-time type is "System String", will have a System Reflection Fieldlnfo object at the time of run-time instantiation, which will be pointing to "Art" variable in the code beside file The properties of the activity which are of type VanableDeclarations or
HandlerDeclarations may also override OnRuntimeInitiahzed() to get informed about the run-time mode The 'Scope ' property on MemberDeclaration will be initialized with the Scope object to which the Member belongs to Also the GetRuntimeValue() and SetRuntimeValue() methods on VanableDeclaration and HandlerDeclaration starts returning the value of the variable or method for a particular instance of the schedule
Writing Custom Activity
To write a custom activity, the activity class inherits from either ActivitDecl or CompositeActivityDecl To support custom serialization of the activity, a SenahzerAttnbute has been added to the activity class A designer attribute associates a designer with the activity Here is a sample activity code
[ToolboxItem(typeof(WorkflowToolboxItem))]
[Designer(typeof(FooActivityDesigner), typeof(IDesigner))]
[ActivityExecutor(typeof(FooExecutor))]
public sealed class FooActivity Activity
{
public FooActivity 0
{ }
private string foo = string Empty, public string Foo
{
get
{
return this foo,
} set
{
this foo = value,
} } }
Sample Program to Use Component Model
Following is a sample code to program against Component model Schedule is the root of object model This sample create a new Schedule enumeration is used to tell the reason for changes into the item list
// create schedule
Schedule schedule = new Schedule(),
schedule NamespaceName = "SampleUserCode",
schedule ID = "MySchedule",
// create a scope
Scope scope = new Scope(),
scope ID = "MyScope",
schedule Activities Add(scope),
// create a send activity which will send something out
Send sendl = new Send(),
sendl ID = "sendl",
sendl Message Name = "msgl",
sendl Message Type = typeof(System String) FullName,
sendl HasTypedChannel = true,
sendl TypedChannel Name = "portl",
sendl TypedChannel Type = typeof(SampleUserCode IFoo) FullName,
sendl TypedChannel Operation = "Foo",
scope Activities Add(sendl),
// create a delay activity which will put a delay in schedule execution
DelayDecl delayl = new DelayDecl(),
delay 1 ID = "delay 1",
delayl TimeoutProvider Name = "delayl_TimeoutProvider",
schedule Activities Add(delayl),
// create a receive activity
Receive receive 1 = new Receive(),
receive 1 ID = "receive 1",
receive 1 Message Name = "msg2",
receive 1 Message Type = typeof(stnng) FullName,
receive 1 HasTypedChannel = true,
receive 1 TypedChannel Name = "port2",
receive 1 TypedChannel Type = typeof(SampleUserCode IFoo) FullName, receive 1 TypedChannel Operation = "Foo", scope Activities Add(receivel),
Xoml Compiler
The Xoml compiler is used to compile Xoml files and generate run-time code for it Errors given by Xoml compiler are presented by XomlCompilerError Also the compiler takes XomlCompilerParameter as input The compiler results are given out by XomlCompilerResults
Xoml compiler deserializes the xoml file and then walks through the activity graph It asks each activity to validate itself in a given context If an activity wants to participate in validation then it inherits from IActivity Validator If there are no validation errors given by any activity then it asks each activity to generate code for itself If an activity wants to participate in code generation then it inherits from IActivityCodeGenerator
XomlCompiler Class
Xoml compilation is different from many other language compilers Xoml compiler takes xoml files, user-code files as inputs and generates run-time process code Following are the steps involved in XomlCompilation
1) Deserialize all the Xoml files and create an activity graph out of it
2) Based on the assembly references, user code files and code compile units passed to the compiler, in form of parameters, create a TypeProvider component
3) Walk through the activity graph of each individual xoml file and call validate on them
4) If there are no validation errors, then call IActivityCodeGeenrator GenerateCode on top most activity for each xoml activity graph, which will generate CodeStatementCollection
5) Either give out a CodeCompileUnit of the process code generated or compile the process code with the passed in user code and build an assembly using C# or VB compiler
Following are the public methods available on XomlCompiler public class XomlCompiler {
XomlCompilerResults CompileFromDom(XomlCompilerParameters parameters,
Schedule scheduleDecl),
XomlCompilerResults CompileFromDomBatch(XomlCompilerParameters
parameters, Schedule[] scheduleDecls),
XomlCompilerResults CompileFromFile(XomlCompilerParameters parameters,
string file),
XomlCompilerResults CompileFromFileBatch(XomlCompilerParameters
parameters, stnng[] files),
XomlCompilerResults CompileFromSource(XomlCompilerParameters parameters,
string xomlSource),
XomlCompilerResults CompileFromSourceBatch(XomlCompilerParameters
parameters, stnngf] xomlSources),
void Generate SkeletonCompanionCode(Schedule schedule, SupportedLanguages
language, System 10 TextWnter writer),
void GenerateSkeletonCompanionCode(stnng file, SupportedLanguages language,
System 10 TextWnter writer),
}
CompileFromDom Method
XomlCompilerResults CompileFromDom(XomlCompilerParameters parameters,
Schedule scheduleDecl), CompileFromDom only takes a single Schedule as input parameter and compile it to generate process code This function facilitates the user who wants to compile one schedule at a time This function internally calls CompileFromDomBatch
CompileFromDomBatch Method
XomlCompilerResults CompileFromDomBatch(XomlCompilerParameters
parameters, Schedule[] scheduleDecls), CompileFromDomBatch takes multiple Schedule as input parameter and compile them to generate process code
CompileFromFile Method
XomlCompilerResults CompileFromFile(XomlCompilerParameters parameters, string file),
CompileFromFile takes a single xoml file as input parameter The second parameter is treated as path to xoml file This function facilitates the user who wants to compile one xoml file at a time This function internally calls CompileFromFileBatch
CompileFromFileBatch Method
XomlCompilerResults CompileFromFileBatch(XomlCompilerParameters
parameters, strmg[] files), CompileFromFileBatch takes multiple xoml files as input and compiles them to generate process code The second parameter is an array of paths to xoml files This function deserializes all the xoml files If a XOML file could not be deserialized then it adds the SeriahzationError to the Errors collection in Compiler Results It calls the CompileFromDomBatch function to do the compilation
CompileFromSource Method
XomlCompilerResults CompileFromSource(XomlCompilerParameters parameters,
string xomlSource), CompileFromSource takes text of Xoml file as input parameter and compiles it to generate process code This function calls the CompileFromSourceBatch to perform the actual compilation
CompileFromSourceBatch Method
XomlCompilerResults CompileFromSourceBatch(XomlCompilerParameters
parameters, stnng[] xomlSources), CompileFromSourceBatch takes multiple sources of xoml files as input parameters and compiles them to generate process code It deserialize the sources to get the activity DOM If there are deserialization errors, then it converts those errors into XomlCompileError and reports them through XomlCompilerResults
GenerateSkeletonCompanion Method
void GenerateSkeletonCompanionCode(Schedule schedule, SupportedLanguages
language, System IO TextWnter writer), This function is used to generate skeleton user Code beside file based on the handler, variable names used in the activity dom This function walks through the activity graph and generates template code for scopes, variables and handlers The second parameter tells the
language which needs to be used to generate code Third parameter is a text writer, which hold buffer on which the generated code will be written
void GenerateSkeletonCompanionCode(stnng file, SupportedLanguages language,
System IO TextWnter writer), This function takes the xoml file path as an input parameter This function deserializes the xoml file and calls the earlier function
XomlCompilerParameters
XomlCompilerParameters has properties to pass in the user code to the compiler Following
is the public interface for XomlCompilerParameter
public class XomlCompilerParameters CompilerParameters
{
bool GenerateCodeCompileUmtOnly { get, set,}
bool GenerateDebugCode { get, set,}
SupportedLanguages LanguageToUse { get, set, }
StrmgCollection LibraryPaths { get, }
IServiceProvider ServiceProvider { get, set,}
IList UserCodeCompileUmts { get,}
StrmgCollection UserCodeFiles { get, }
}
GenerateCodeCompileUmtOnly Property
bool GenerateCodeCompileUmtOnly { get, set,} This flag is used to tell the compiler that the user is only interested in generating CodeCompileUnit and not the executable or dll In this case compiler does not call C# or VB compiler to generate code
GenerateDebugCode Property
bool GenerateDebugCode { get, set,} This flag is used to tell if debug code should be used or not
LanguageToUse Property
SupportedLanguages LanguageToUse { get, set, }
There are at least two languages supported VB and C Sharp Compiler needs to know the language to use, because it has many validations based on the language
LibraryPaths Property
StnngCollection LibraryPaths { get,} This is the collection of directory names under which compiler will probe for referenced assemblies Please note that the compiler also adds some standard library paths to this collection for resolving assembly references This behavior is similar to CSharp and VB compiler
ServiceProvider Property
IServiceProvider ServiceProvider { get, set,} This property is only used when the compiler is invoked from a project system The purpose of this property is to achieve performance when the compile is invoked from project system As project system has a TypeProvider created on a per project basis, the compiler uses the same TypeProvider This increases the performance of the compiler significantly when invoked from project system
UserCodeCompileUnits Property
IList UserCodeCompileUnits { get,} This property is used to pass in the Code compile units of the user code beside file to the Compiler
UserCodeFiles Property
StnngCollection UserCodeFiles { get,} This property is used to pass file paths of the user code beside file to Compiler
XomlCompilerResults
XomlCompilerResults has a property to retrieve CodeCompileUnit of the generated process code Following is the public interface of XomlCompilerResults public class XomlCompilerResults CompilerResults
{
CodeCompileUnit CompiledUnit { get, set, }
}
The Compiled Unit property gives access to the process code
XomlCompilerError
XomlCompilerError has a method to get the UserData property, which is of Dictionary type A purpose of this property is to insert extra details about the error For an example, if one of the property validations failed on an activity, will have a property name with typeof(stnng) as the key to dictionary Following is the public interface exposed by this class
public class XomlCompilerError CompilerError
{
System Collections IDictionary UserData { get,}
} XomlCompilerError also implements IWorkflowError interface, the purpose of this interface is to provide COM inter-operability for errors Following is the definition of IWorkflowError interface
public interface IWorkflowError
{
String Document { get,}
bool Is Warning { get,}
String Text { get,}
String ErrorNumber { get,}
int LineNumber { get,}
int ColumnNumber{ get, }
} The properties are mapped to the properties of CompileError class defined in
System CodeDom
Validation Infrastructure
Every activity inherits from IActivity which has a Validate method Validate methods take an IServiceProvider For an example, ITypeProvider determines whether a type name which is an activity's property may be resolved into an actual type or not The validate method returns a collection of IVahdationError Following is the signature of Validate method
IVahdationError[] Vahdate(IServiceProvider context),
Following are the public method available on IVahdationError public interface IVahdationError
{
string ErrorText {get,}
IDictionary UserData {get,}
}
Sample Validation Routine
The following is an example of DelayDecl activity's validation routine Delay wants to validate that the TimeoutProvider handler is actually not null and the method name exists in the parent scope class
public override IValidationError[] Vahdate(IServiceProvider context)
{
ArrayList vahdationErrors = new ArrayList(base Vahdate(context)),
// validate TimeoutProvider property
vahdationErrors AddRange(this TimeoutProvider Vahdate(context, this,
"TimeoutProvider")),
return (IValidationError[])vahdationErrors ToArray(typeof(IVahdationError)),
} And following is the validation routine of HandlerDeclaration
public override IVahdationError[] Vahdate(IServiceProvider context, IActivity
activityDecl, string propName)
{if (context == null) throw new ArgumentNullException("context"),
if (activityDecl == null) throw new ArgumentNullException("activityDecl"),
ArrayList vahdationErrors = new ArrayList(),
string message = string Empty,
if (this Name == null || this Name Length == 0)
{message = SR GetStnng(SR Error_PropertyNotSet, propName),}
else
{ string methodName = string Empty,
Type resolvedType = XomlVahdationHelper ParseInputName(context, activityDecl, this Name, out methodName), if (resolvedType == null)
{message = SR GetStnng(SR Error_TypeNotResolvedInMethodName, propName),} else {// get the invoke method
Methodlnfo invokeMethod = this RuntimeType GetMethod("Invoke"), if (invokeMethod == null) throw new
Exception(SR GetStnng(SR Error_DelegateNoInvoke, this RuntimeType FullName)), // resolve the method
List paramTypes = new List(), foreach (Parameterlnfo paramlnfo in invokeMethod GetParameters())
paramTypes Add(paramInfo ParameterType), BmdmgFlags bindmgFlags = BvndingFlags Public | BindmgFlags Instance | BindmgFlags NonPubhc | BindmgFlags Static,
Methodlnfo methodlnfo = resolvedType GetMethod(methodName, bindmgFlags, null, paramTypes ToArray(), null), if (methodlnfo == null)
{if (resolvedType GetMethod(methodName, bindmgFlags) '= null) message=SR GetStnng(SR ErrorMethodSignatureMi smatch, propName), else message = SR GetStnng(SR ErrorMethodNotExists, propName, methodName),}
else if ('invokeMethod ReturnType Equals(methodInfo ReturnType))
{message = SR GetStnng(SR Error_MethodReturnTypeMismatch,
propName, invokeMethod ReturnType FullName),}}}
IVahdationError error = null,
if (message Length > 0)
{ error = new VahdationError(message),
error UserData[typeof(stnng)] = propName, validationErrors Add(error),} return (IVahdationError[])vahdationErrors ToArray(typeof(IVahdationError)),}
Runtime Code Generation
The Xoml compiler generates a Schedule class with the namespace as the NamespaceName property on the schedule and class name as ID property on the schedule Then it serializes the Schedule object into a xoml string and annotates the schedule class with XomlAttnbute on it, with the first parameters being the xoml string
The following sample code creates a Schedule Decl object and also creates a CodeCompileUnit object which contains the user code It also gives the Schedule object and the UserCode to Xoml compiler
In particular, the following code creates a schedule
Schedule schedule = new Schedule(),
schedule NamespaceName = "SampleUserCode",
schedule ID = "MySchedule",
Scope scope = new Scope(),
scope ID = "MyScope",
schedule Activities Add(scope),
Send sendl = new Send(),
sendl ID = "sendl",
sendl Message Name = "msgl",
sendl Message Type = typeof(System String) FullName,
sendl HasTypedChannel = true,
sendl TypedChannel Name = "portl",
sendl TypedChannel Type = typeof(SampleUserCode IFoo) FullName,
sendl TypedChannel Operation = "Foo",
scope Activities Add(sendl),
Receive receive 1 = new Receive(),
receive 1 ID = "receive 1",
receive 1 Message Name = "msg2",
receive 1 Message Type = typeof(stnng) FullName,
receive 1 HasTypedChannel = true,
receive 1 TypedChannel Name = "port2",
receive 1 TypedChannel Type = typeof(SampleUserCode IFoo) FullName,
receive 1 TypedChannel Operation = "Foo",
scope Activities Add(receivel),
DelayDecl delay 1 = new DelayDecl(),
delay 1 ID = "delay 1",
delayl TimeoutProvider Name = "delayl_TimeoutProvider",
schedule Activities Add(delayl),
The code below creates a code compile unit, adds a namespace, adds a MySchedule Class, and adds a delay method
CodeCompileUnit ecu = new CodeCompileUmt(),
CodeNamespace sampleUserCode = new CodeNamespace("SampleUserCode"),
ecu Namespaces Add(sampleUserCode),
/*
public partial class MySchedule Schedule
{
public MySchedule()
{
} }
*/
CodeTypeDeclaration mySchedule = new CodeTypeDeclaration("MySchedule"), mySchedule BaseTypes Add(new
CodeTypeReference("System Workflow Runtime Schedule")), mySchedule IsClass = true, mySchedule PartialType = PartialType Partial, mySchedule TypeAttnbutes = TypeAttnbutes Public, sampleUserCode Types Add(mySchedule), /* public System DateTime delay l_TimeoutProvider()
{
return new System DateTime(),
}
*/
CodeMemberMethod delayMethod = new CodeMemberMethodQ,
delayMethod Name = "delay l_TimeoutProvider",
delayMethod Attributes = (MemberAttnbutes Public | MemberAttnbutes Final),
delayMethod ReturnType BaseType = typeof(System DateTime) FullName,
delayMethod Statements Add(new CodeMethodReturnStatement(new
CodeSnippetExpression("new System DateTime(),"))),
my Schedule Members Add(delayMethod),
The code shown below writes a MyScope class and adds a field
/*
public partial class MyScope Scope
{
}
*/
CodeTypeDeclaration myScope = new CodeTypeDeclaration("MyScope"),
myScope BaseTypes Add(new
CodeTypeReference("System Workflow Runtime Scope")),
myScope IsClass = true,
myScope PartialType = PartialType Partial,
myScope TypeAttnbutes = TypeAttnbutes Public,
sampleUserCode Types Add(myScope),
/*
public System Workflow Runtime OEMessage msgl,
public System Workflow Runtime OEOutboundChanneKSampleUserCode IFoo>
portl,
public System Workflow Runtime OEMessage msg2,
public System Workflow Runtime OEInboundChannel port2,
*/
CodeMemberFieldmsgl =new
CodeMemberField("System Workflow Runtime OEMessage",
"msgl"),
msgl Attnbutes= MemberAttnbutes Public,
myScope Members Add(msgl),
CodeMemberField portl = new
CodeMemberField("System Workflow Runtime OEOutboundChanneKSampleUser
Code IFoo>", "portl"),
portl Attributes = MemberAttnbutes Public,
my Scope Members Add(portl),
CodeMemberField msg2 = new
CodeMemberField("System Workflow Runtime OEMessage",
"msg2"),
msg2 Attnbutes = MemberAttnbutes Public,
myScope Members Add(msg2),
CodeMemberField port2 = new
CodeMemberField(" System Workflow Runtime OEInboundChanneKSampleUserC
ode IFoo>", "port2"),
port2 Attributes = MemberAttnbutes Public,
myScope Members Add(port2),
The code below generates the final C# code In particular, the code combine the CCUs from the User code and the CCU of the XOML OM to generate the assembly
XomlCompiler compiler = new XomlCompiler(),
XomlCompilerParameters parameters = new XomlCompilerParameters(),
parameters ReferencedAssembhes Add(typeof(SampleUserCode IFoo) Assembly L
ocation),
parameters UserCodeCompileUmts Add(ccu),
parameters OutputAssembly =
@"c \CreateAssemblyWithUserCodeInCodeDOM dll",
XomlCompilerResults results = compiler CompileFromDom(parameters, schedule),
Error Navigation Infrastructure
When the Xoml compiler is invoked, it returns the collection of IWorkflowError objects if there are any errors For each IWorkflowError object, a task item is created Following are the steps involved to navigate to the error on to the designer, when user double clicks the task item
1) Each task item is associated with a IWorkflowError object
2) On double clicking first, it gets the name of the file by calling IWorkflowError Document property
3) It asks the designer to Open the file and get the DocView object associated with it
4) It looks IWorkflowErrorNavigator interface on to the DocView
5) It calls IWorkflowErrorNavigator Navigate() method, and passes the IWorkflowError as the first parameter
6) IWorkflowErrorNavigator interface is implemented on the document view object In the Navigate method's implementation, the editor tries to look for "typeof(IActivity)" object in the UserData property of IWorkflowError, if found it gets the scope qualified name of the activity and searches for the activity with the same name in the designer If an activity is found it is focused After that it looks for 'typeof(stnng)' key in the UserData property if found it assumes it should be the name of the property which needs to be focused, so it calls
IExtUIService NaviagteToProperty() method by passing property name as first argument Following is the interface definition of IWorkflowErrorNavigator internal interface IWorkflowErrorNavigator
{
void NavigateToError([MarshalAs(UnmanagedType IUnknown)] object obj),
}
Workflow Compiler Executable (aka WFC EXE")
Wfc exe is a product binary which is a command line version of XomlCompiler This executable parses the command line arguments and fills up the XomlCompilerParameters structure
Following are the definitions of the options which may be passed to the XomlCompiler
wfc exe xoml /target codebeside [/language ]
wfc exe xoml /target xomlclass [/language ]
wfc exe xoml /target assembly [ cs] [/language ] [/out ] [/reference ] [/library ] [/debug ]
- OUTPUT FILE -
/out Output file name
/target assembly Build a Workflow assembly (default)
/target xomlclass Generate partial class definition /target codebeside Generate skeleton codebeside
- INPUT FILES -
Xoml source file name(s)
Codebeside file name(s)
/reference Reference metadata from the specified assembly file(s)
Short form is 7r ' /library Set of directories where to lookup for the references
Short form is '/lib '
- CODE GENERATION -
/debug [yes|no] Emit full debugging information The default is 'yes'
Short form is Vd ' /skipvahdation[+|-] Skip workflow validation /emitruntimecode[+|-] Emit Runtime Code for the workflows
- LANGUAGE -
/language [cs|vb] The language to use for the generated class
The default is 'CS' (CSharp) Short form is VI' /rootnamespace Specifies the root Namespace for all type declarations
Valid only for 'VB' (Visual Basic) language
- MISCELLANEOUS -
/help Display usage message Short form is 'P'
/nologo Suppress compiler copyright message Short form is Vn'
Type System
The Type system is an independent component in the designer CodeCompileUnit and assemblies may be pushed to the type system It loads the System Type objects from an assembly reference and pushes them to the type tree Also for each CodeTypeDeclaration object in CodeCompileUnit it creates DesignTimeType which inherits from System Type and pushes them to the type tree This way the types from the type system are exposed by a common abstract class System Type Like many other type systems, it creates a tree structure on loading types into it, which makes the type resolution very fast Type system provides a user interface over the type tree to resolve types, also, it fires events to notify about changes in the type tree
Following are the major components in the Type System
1 TypeProvider It has public methods to add/remove assembly references and
CodeCompileUnit to the Type system Also, it implements an interface which
exposes the type tree to the user
a TreeNode Tree node is a general node in type tree It keeps all the type definitions associated with it
2 CodeDOMLoader CodeDOM Loader loads all the types from Code Compile Unit and pushes them to the Type Tree On disposing the CodeDOM loader it removes all the types which it added to type tree
3 AssemblyLoader Assembly loader loads all the types form an assembly and pushes all the types to the type tree On disposing this it will remove all the types from type tree
4 DesignTimeType This class inherits from System Type It takes CodeTypeDeclaration CodeDOM construct as its constructor argument and implements all the properties and methods of System Type class Also following classes are used to convert from CodeTypeDeclaration to System Type
a DesignTimeMethodlnfo This class is used to implement all the members of
Methodlnfo based on the CodeMemberMethod
I DesignTimeParamterlnfo This class inherits from Parameterlnfo and provides implementation based upon CodeParameterDeclarationExpression Code DOM construct b DesignTimeEventlnfo this class is used to implement members of Eventlnfo
based on CodeMemberEvent c DesignTimeFieldlnfo This class inherits from Fieldlnfo and provides
implementation of all the methods and properties based on
CodeMemberField d DesignTimePropertylnfo this class inherits from Propertylnfo and provides
implementation of all the methods and properties based on
CodeMemberProperty code dom construct e DesignTimeConstructorlnfo This class inherits from Constructorlnfo and
provides implementation of all the method and properties based on
CodeMemberMethod f Attnbutelnfo Attnbutelnfo class is used to hold information about the
attributes on the types
Type Provider Component
Type provider is a top level component in type system An instance of type provider may be created Type provider keeps a root node of the type tree On adding assembly references and code compile units to the type provider, it loads all the types from them and loads them to the Type Tree
For an example here If you have following types coming from an assembly Art Bar Zoo Art Peter Baz System String Then the corresponding tree structure looks like Art
--Bar
—Zoo
- Peter
-Baz System
- String
Each node keeps a list of type definitions which it points to For an example in the above scenario String node will contain System String type A list of type definitions is kept on each node There may be duplicate types in the type system The following are the public methods of Type provider
AddAssemblvReference Method
public void AddAssemblyReference(stnng path) This method is used to Add assembly references to the type system All the types from the assembly will be loaded on to the type system
RemoveAssemblyReference Method
public void RemoveAssemblyReference(stnng path) This method is used to Remove assembly references from the type system All the types loaded from this assembly to the type tree will be removed
AddCodeCompileUmt Method
public void AddCodeCompileUmt(CodeCompileUnit codeCompileUmt)
This method is used to load CodeCompileUmts to the type system This will go through all the CodeTypeDeclarations in the code compile unit and will create appropriate DesigntimeType which inherits from System Type for each one of them And DesignTimeType will be loaded to the type system
RemoveCodeCompileUmt Method
public void RemoveCodeCompileUnit(CodeCompileUnit codeCompileUnit) This method is used to unload CodeCompileUnit from type system All the types loaded from CodeCompileUnit will be removed
RefreshCodeCompileUnit Method
public void RefreshCodeCompileUnit(CodeCompileUnit codeCompileUnit,
CodeCompileUmtRefreshHandler refresher) This method is used to refresh the Code compile unit in the type system It is like removing a compile unit from type system and then adding it back to the type system
ITypeProvider Interface
This service is used to access and resolve types in the hosting environment's type system This is the interface exposed by the TypeProvider component ITypeProvider is the interface exposed by the TypeProvider to the user It is used to resolve types in the type system Following is the definition of this interface
public interface ITypeProvider
{
Type GetType(stnng name),
Type GetType(stnng name, bool throwOnError),
Type[] GetTypes(),
StnngCollection TypeLoadErrors
{
get,
}
event EventHandler TypesChanged,
event EventHandler TypeLoadErrorsChanged,
}
Following is a description of the components involved in hosting TypeProvider in the designer
TypeProviderHost Component
TypeProviderHost is the main component used for maintaining TypeSystem on a per project basis TypeProviderHost keeps a project system pointer and a corresponding TypeProvider It pushes one CodeCompileUnit to TypeSystem by parsing all the user code files Also it listens to all the project system events which may modify types contained in the type system Following are the architectural work done by the TypeProviderHost
1 Parse User Code files and create a CodeCompileUnit (FileCodeModel to CodeDOM layer)
2 Listens to events in project system and make appropriate calls to the TypeProvider to refresh types
Here is the list of events it listens for and the corresponding TypeProvider call it makes to notify about the changes
ILangFileEvents These events are tracked for the file add, remove, move , build action change etcetera in the project When any of these event happen, the type provider refreshes the CodeCompileUnit
dispCodeModelE vents These events are fired by file code model of Visual basic whenever a new CodeElement is added to user code file These events are only meant for visual basic project system, similar events are not fired in a C# project system
dispReferencesEvents These events are fired on adding or removing an assembly reference from the project On getting an add assembly reference event, the assembly is added to corresponding TypeProvider On getting a remove assembly reference event, the assembly reference is removed from the type system
dispBuildEvents Build events are tracked for project-project to reference cases In such cases when a referenced project is built, the old assembly is removed from type system and the new assembly is refreshed into the TypeProvider to load new types from it
IVsRunningDocTableEvents Running document table events are tracked for multiple purposes For example, when a document is changed in editor but closed without saving it, the type system is reverted back to the non-saved state because the type system was updated with the changes in the file When a document is opened m an editor for editing, the invention listens for IVsTextStreamEvents to get these events and refresh the code compile unit
IVsTextStreamEvents These events are used to listen to file editing done by the user
ITypeProviderCreator Service
The ITypeProviderCreator service is exposed on a designer package level Using this service one may get the TypeProvider for a project Following is the interface definition of ITypeProviderCreator
public interface ITypeProviderCreator
{
ITypeProvider GetTypeProvider(object obj),
} This service is implemented by the orchestration designer package The implementation of
this service listens to IVsSolution events and maintains a type provider host for each project in the solution Also this service creates a TypeProviderHost for a project when someone demands it for the first time Using this service, a developer gets to the TypeSystem of any project Also on solution close, this service destroys all the TypeProviderHost in the system On closing a project, this service removes the corresponding TypeProviderHost from the system
The orchestration engine toolbox page buffers the toolbox entries categorized by assembly m a binary file When activated, these entries are loaded into the page The items in the toolbox are checked to indicate that if they are shown by the toolbox The User may add new toolbox items from different assemblies by choosing the browse button The Browse button brings up File Select dialog in which the user selects an assembly from which additional toolbox items may be loaded The toolbox page loads the user chosen assembly in a separate app-domain and gets all the toolbox items out of it by calling ToolboxService GetToolBoxItems These items are then marshaled across domains and loaded into the toolbox page This is done so that the user assemblies are not loaded into the primary domain and locked The User then may check and uncheck the toolbox items which need to be shown in the toolbox When the dialog is closed the toolbox page uses ToolboxService AddToolBoxItems and ToolboxService RemoveToolBoxItems to add and remove items from the toolbox based on their checked state The toolbox page also serializes the updated toolbox entries in a binary file so that they may be loaded the next time toolbox page is shown
GetType Method
Type GetType(strmg name), This method is used to resolve type in type Tree The User passes in a string in the form of "A B C" where A B is the namespace and C is the name of type in the namespace This method could return "null," which means that type with the following name could not be resolved
GetType overload Method
Type GetType(stnng name, bool throwOnError), This method is identical to the above method, only difference is that it throws an exception when a type is not found
GetTypes Method
Type[] GetTypes (), This method is used to retrieve all the types present in the type system
TypeLoadErrors Property
StnngCollection TypeLoadErrors {get,} On loading types on to the Type provider, it might get into some problems, for an example it could not resolve an assembly reference In those scenarios TypeLoadErrors property returns all the type load errors
TypesChanged Event
event EventHandler TypesChanged, Whenever a new assembly reference or code compile unit is added to the Type System, this event will be fired to the user telling that types in the type system are changed This is a general event which means it does not provide any specific information on which types are added or removed
Delay Loading Infrastructure
Type system has delay-loading capabilities Assembly references and CodeCompileUnits added to TypeProvider are not loaded until some one needs to resolve types from the type tree So the code m AddAssemblyReference and AddCompileUmt caches the assembly paths and CodeCompileUnit and fires the TypesChanged event None
of the types will be loaded until and unless someone demands for them This technique improves the performance of type system Due to this reason, exceptions are not thrown when the type loading fails Instead, TypeLoadErrors are fired
The following code snippet explains how to create TypeProvider component
// create code compile unit
CodeCompileUnit ecu = new CodeCompileUnit(),
// add namespace
CodeNamespace sampleUserCode = new CodeNamespace("SampleUserCode"),
ecu Namespaces Add(sampleUserCode),
CodeTypeDeclaration mySchedule = new CodeTypeDeclaration("MySchedule"),
mySchedule BaseTypes Add(new
CodeTypeReference("System Workflow Runtime Schedule")),
mySchedule IsClass = true,
mySchedule PartialType = PartialType Partial,
mySchedule TypeAttnbutes = TypeAttnbutes Public,
sampleUserCode Types Add(mySchedule),
// create a Type Provider
TypeProvider typeProvider = new TypeProvider(null),
typeProvider AddAssemblyReference(Assembly GetExecutingAssemblyO Location
)
typeProvider AddCodeCompileUnit(ccu),
XomlSeriahzer Class
The senahzer component associated with an activity inherits from XomlSeriahzer XomlSeriahzer is also a default senahzer component for the activities It reflects over the activity properties and serializes them For the composite activities, the default senahzer component is CompositeXomlSenahzer, which in addition to primitive Xoml serialization, also serializes the child activities
The functions in this class may be further categonzed as public functions which are used to serialize and deserialize the xoml file, functions which are used to control senahzation of an object, and functions which are used to control deserialization of an object
Public Functions to Senalize/Desenahze XOML File
public object Desenahze(XmlTextReader reader) This method, given a XmlTextReader object, deserializes it and returns an object XmlTextReader is pointing to an xml element This is a public method to deserialize the xoml file
public object Desenalize(IDesignerSenalizationManager sm, XmlTextReader reader)
This method deserializes an activity given a TextReader and
IDesignerSenahzationManager The IDesignerSeriahzationManager object may be used to provider custom deserializer for objects and also to resolve the types
public void Senahze(object obj, XmlTextWnter writer) This method serializes the object specified in the first parameter to the XmlTextWnter object
public void Serialize(IDesignerSeriahzationManager sm, object obj, XmlTextWnter wr),
This method serializes the object onto the XmlTextWnter object It takes an additional designer serialization manager object which may be used to resolve type etcetera
Deserializing an Obiect
protected object DeseriahzeObject(IXomlSenalizationManager sm, XmlTextReader rd),
This method deserializes an element and creates an object It uses the xmlns to CLR namespace and assembly mapping to resolve the type of the object and then gives a chance to the senahzer component associated with the type to create the instance of the type The Createlnstance method of the XomlSenahzer is used to create instance of the object, which may be ovemdden in derived classes The XmlTextReader must be pointing to an element node otherwise this method throw an exception This method calls the DesenahzeContents after creating the instance of the object
protected void DesenalizeContents(IXomlSerializationManager sm, object obj,
XmlTextReader rd), This method is used to deserialize properties and child objects of an object It takes the object and the XmlTextReader as parameters XmlTextReader points to the XmlElement node It goes through all the attnbutes of the element and calls DesenahzeSimplePropertyO on the senahzer The DeseriahzeSimpleProperty may be overridden to do custom deserialization of properties After that it goes through all the child elements of the element
and recognizes them either as child objects or properties On realizing a child element as property it calls DesenalizeCompoundProperty() on the senahzer, otherwise it calls DeserializeObject() to deserialize the child element and adds the returned object as the child of the main object To to add the returned object as the child object it calls AddChild() method on the senahzer which may be overridden to implement different parent-child relation ships
protected virtual void DesenalizeSimpleProperty(IXomlSeriahzationManager sm,
object obj, XmlTextReader rd), This method is called by DesenahzeContents() to deserialize a simple property The object of which the simple property is part of and the XmlTextReader is passed as parameters The XmlTextReader points to an attribute The name of the attribute is treated as the name of the property
protected virtual void DesenahzeCompoundProperty(IXomlSerializationManager
sm, object obj, PropertyDescnptor pd, XmlTextReader rd), This method is called by DesenahzeContents() to deserialize a compound property It is passed the object, proerty descriptor and the XmlTextReader The XmlTextReader points to the XmlElement The property could be a readonly or non-readonly If the property is readonly then the getter method on the property is called which will give the object, now the DesenahzeContents on that object is called to deserialize the contents of the object If the property is read-write then it may only have one and only one child element The first child element is deserialized and the returned object is set on the property
Serializing an Obiect
protected void SenahzeObject(IXomlSeriahzationManager s, object o,
XmlTextWnter wr), This method is called to serialize the object It is passed the object which needs to be serialized and the XmlTextWnter on which the serialization contents have to be written This method constructs XmlQuahfiedName for the object, which actually is the xml namespace and class name of the type of the object The xml namespace is constructed using the assembly and namespace information of the type of the object It wntes the begin of an xml element with that qualified name and then calls SenahzeContents() to further serialize the properties and child objects of the object And it calls the EndElement to close the element
protected void SenahzeContents(IXomlSenalizationManager s, object o,
XmlText Writer w), This method is called to serialize all the properties and child objects of an object This method is passed the object and the XmlTextWnter which points to an Xml element It looks for the senahzer component of the object and calls GetProperties() on it to get the properties of the object It looks for DesignerSenahzationVisibility attribute on property, if the Visibly is set to Visible then property is treated as simple property and SenahzeSimpleProperty is called, if the Visibility is set to Content then property is treated as complex property and SenahzeCompoundPropertyO is called, otherwise if the visibility is set to Hidden then the property is ignored Also it checks for DefaultValue attribute for the property, if the DefaultValue of the properly is same the value of the property then the property is skipped It calls GetChildren() on the senahzer component of the object to get all the children objects It then serializes all the child objects using SenahzeObject()
protected virtual void SenalizeSimpleProperty(IXomlSenalizationManager sm,
object obj, PropertyDescnptor pd, string parentPropName, XmlTextWnter wr), This method is passed the object of which the property needs to be serialized, the PropertyDescnptor of the property and XmltextWriter object This function writes an xml attribute on the XmlTextWnter byusing the property name as the attribute name and property value as the attribute value
protected virtual void SeriahzeCompoundProperty(IXomlSenalizationManager sm,
object obj, PropertyDescnptor pd, XmlTextWnter wr), This method is used to senahze a compound property of an object It is passed in an object, the property descriptor and the XmlTextWnter object If the property is read-only it creates an element and calls SenahzeContents() on the object returned by the property's getter method call, otherwise it writes an start element whose name is the name of the property and calls SenahzeObject() on the object returned by the property's getter method call
Helper Functions
protected virtual IList GetChildren(object obj), This method is used to get the child objects of an object Usually objects use different mechanisms to describe the parent child relation ships For an example the ICompositeActivity denotes the child objects programmatically using the Activities property The different senahzer may overnde this property and return the list of child objects By default this returns value
protected virtual PropertyDescnptorCollection GetProperties(object obj), This method is used to get properties of an object By default this method returns the properties with Browsable attribute set to true and DesignerSenahzationVisibility attribute not set to Hidden The object senahzer component may override this and control the collection of returned properties
protected virtual void AddChild(object obj, object childObj), This method is used to add a child of the parent object It does the reverse of GetChildren(), The senahzer component may control the behavior of the AddChild() implementation
protected virtual object CreateInstance(Type type, XmlTextReader rd), This method is used to create an instance of the type By default it calls Activator CreatelnstanceQ to create the object But the derived classes may use different techniques to Createlnstance() of their component types and they may also pass some parameters on the constructor by using the XmlTextReader object
CompositeXomlSenalizer Class
Composite Xoml senahzer is used to serialize composite activities It has two methods overndden from base class for deserializing and senahzmg child activities
public class CompositeActivityXomlSenahzer XomlSenahzer
{
protected override IList GetChildren(object obj)
{
argument checks ICompositeActivity compositeActivity = obj as ICompositeActivity, return (IList)compositeActivity Activities,
}
protected override void AddChild(object obj, object childObj)
{
argument checks ICompositeActivity compositeActivity = obj as ICompositeActivity, IActivity activity = childObj as IActivity, compositeActivity Activities Add(activity), } }
IXomlSenalizationManager Interface
IXomlSeriahzationManager inherits from IDesignerSenalizationManager class It provides additional functions to give the activity type given an xml qualified name and vice-versa Following is the interface definition of IXomlSeriahzationManager
public interface IXomlSeriahzationManager IDesignerSenalizationManager
{
XmlQualifiedName GefXmlQualifiedName(Type type),
Type GetType(XmlQuahfiedName xmlQuahfiedName),
}
Serialization Errors
Xoml senahzer adds all the Deserialization errors using the IDesignerSenalizationManager ReportError() method When ever the desenahzation encounters an error it simply adds the error object, but it does not stop the desenahzation process until and unless the xml format is illegal The XomlSenahzer reports the deserialization errors using XomlSenahzerException class
public class XomlSenahzationException Exception
{
private int hneNumber = -1, private int columnNumber = -1,
public XomlSenalizationException(stnng message, int line, int column) base(message)
{
}
public XomlSeriahzationException(stnng message, Exception mnerException, int
line, int column)
{
}
public XomlSenalizationException(stnng message)
{ }
public int LineNumber { get,} public int LinePosition { get,}
} The workflow componentModel also provides serialization of a schedule to a web services
description language (WSDL) format
Orchestration Engine Designer Architecture
The orchestration engine designer uses the classes defined in the System ComponentModel and System ComponentModel Design namespaces The framework infrastructure classes used by the orchestration engine designer are DesignSurface, DesignSurfaceManager and DesignerLoader All of these classes are part of System ComponentModel Design namespace
The following table briefly describes the description and uses of this namespace
Namespace System Workflow ComponentModel Design
Description This namespace contains implementation of all the activity
designers and interfaces used by the orchestration engine
designer
Uses • Contains base classes for writing the designers
• Contains Interfaces for plugging in the activity designers into the orchestration engine designer
• Contains plumbing needed to talk with classes in System ComponentModel Design namespace
• Classes useful in writing custom activity designers
• Classes useful in writing custom toolbox items so that activities may appear in toolbox
Binary System Workflow ComponentModel dll
Table B2 System Workflow ComponentModel Design
DesignSurface and DesignSurfaceManager
DesignSurface represents a designer, and includes a default set of services that will be needed by designers DesignSurfaceManager provides essentially a collection of designers, along with some application-level services those designers may use for communication purposes DesignSurface exposes multiple services using IServiceProvider interface The master service exposed is IDesignerHost IDesignerHost keeps a collection of
components added to it, and creates designer for all the components added to it, based on the DesignerAttnbute declared on the component Every component added to designer host must inherit from IComponent Also the first component added to it is known as RootComponent The designer for RootComponent must implement an interface called IRootDesigner This interface has a method called GetView(), which returns 'Control' object for the root component The design surface returns the Control returned by root component's GetView() m its view property implementation
The orchestration engine designer uses Schedule as RootComponent and ServiceRootDesigner as its root designer The GetView() method on ServiceRootDesigner returns 'WorkflowView' control, which may be directly hosted by the hosting environment, for an example when the orchestration engine designer is hosted in the designer, the WorkflowView control will be hosted by IVsWmdowPane's primary window
DesignerLoader
DesignerLoader is an abstract class responsible for deserialization and serialization of object graph A designer loader is created and handed a file or blob of data that contains the serialized state for the designer The relationship between the data and the loader is private to the loader's implementation The designer loader is asked to begin the loading process It is passed an interface pointer, called IDesignerLoaderHost that provides access to DesignSurface that knows how to create designers IDesignerLoaderHost also provides some common utility functions The designer loader interprets its bag of serialized data It creates instances of components, adds them to the container, and sets properties on them The orchestration engine designer has ServiceDesignerLoader as its implementation for for DesignerLoader class
Journey from Xoml File to WorkflowView control
Following is the pseudo code which explains how to hook together all these infrastructure pieces to deserialize the Xoml and display it in a Window Form control
DesignSurface surface = new DesignSurface(),
ServiceDesignerLoader loader = new ServiceDesignerLoader(surface),
loader FilePath = "c Wfoo xoml",
surface BeginLoad(loader),
Control control = surface View,
The above code first creates a DesignSurface Then it creates a DesignerLoader and passes the surface object in its constructor Then it sets the FilePath property on the loader Now it asks the surface to start loading using the specified loader DesignSurface in turn calls DesignerLoader BeginLoad() to load the xoml file This causes the activities to be added to DesignSurface, which in turn creates a designer for these activities and caches the activities and their designers The first component added is Schedule which is known as RootComponent and it has the ServiceRootDesigner associated as a designer using DesignerAttnbute
IComponent and IComponent Site
All the components added to DesignSurface implements IComponent DesignSurface creates a Site object and sets it on IComponent Site property When a component is sited, it is said to be "owned" by a particular container A container may provide services to the component through the component's site, and the container itself may even delegate service requests to a parent service provider
IDesigner and IActivitvDesigner
The components added to design surface have a designer associated with them which implements IDesigner interface IDesigner interface is primitive and the functionality provided is common to all the components To host designer in the orchestration engine DesignSurface, it must implement IActivityDesigner, which is an interface defined to do most of the UI related work For an example drag/drop, mouse, keyboard, lay-outing, rendering etcetera Designers are associated with components through a class-level attribute of type DesignerAttnbute Designers are created by a special implementation of the IContainer interface When a component is added to this container, the container will search the component's metadata for a designer attribute If it exists, the designer will be created and initialized
Design Time Services Requirements
Every designer is initialized with the IComponent it is associated with IComponent Site allows the designer to communicate through the outer world When a component is added to IDesignerHost, designer host creates a site for the component and set it on IComponent Site property Site inherits from IServicePovider which allows the designer to access the outer world services
Services Proffered by DesignSurface
These are standard services proffered by DesignSurface
(Table Removed)
Table B3 Services Offered by the Designer Services Proffered by Hosting Environment
(Table Removed)

Table B4 Services Offered by the Hosting Environment
Workflow View
Workflow view is the design surface which renders a visual representation of process flow described in XOML Workflow view offers rich set of UI functionality needed by the activity designers for rendering and for responding to various windows generated events In addition to this the workflow view offers set of common functions which may be used by all the designers to perform certain activities
public class WorkflowView UserControl, IDesignerService, IDesignerView,
IServiceProvider
System Object System MarshalByRefObiect System ComponentModel Component System Windows Forms Control System Windows Forms ScrollableControl System Windows Forms ContainerControl System Windows Forms UserControl[Visual Basic]
System OrchestrationEngine ComponentModel Design WorkflowView
UserControl User control allows the workflow view to be rehosted into a third party
application to render the workflow
IDesignerService The designer service enables the workflow view to expose functionality
which enables the activity designers and other hosts to interact with it to exploit various user
interface features
IDesignerView The designer view interface allows the workflow view container to interact
with workflow Using this service the outer container may communicate its active state to
the workflow view which in response to these messages updates its UI state and may do
initializations
IServiceProvider workflow view acts as service provider to the activity designers, using the
workflow view the activity designers may get access to other services proffered in service
container
Workflow view is the design surface which renders a visual representation of process flow described in XOML Workflow view offers rich set of UI functionality needed by the activity designers for rendering and for responding to various windows generated events In addition to this the workflow view offers set of common functions which may be used by all the designers to perform certain activities.

We Claims :-
1 A computerized system for authoring a workflow, said workflow modeling a business
process, said computerized system comprising
a package identifying a plurality of activities associated with a workflow,
an interface for selecting and interrelating one or more of the plurality of activities,
and
a senahzer for serializing the identified activities to create a persistent representation
of the workflow
2 The computerized system of claim 1, further comprising
a design application programming interface for authoring the workflow, wherein each of the plurality of activities has a component model associated therewith, said component model specifying properties of the activity associated therewith, and
a compilation application programming interface for compiling the workflow authored via the design application programming interface
3 The computerized system of claims 1-2, wherein
the specified properties comprise one or more of the following design time behavior, compile time behavior, and run time behavior, and
the plurality of activities includes a user-defined activity, said user-defined activity having one or more properties, and further comprising a semantic checker for verifying a format associated with each of the properties
4 The computerized system of claims 1-3, wherein the interface receives software code that implements business logic associated with the selected activities, further comprising a compiler for compiling the serialized workflow representation and the software code into an executable representation of the workflow, and further comprising a runtime engine for executing the executable representation of the workflow created by the compiler
5 The computerized system of claims 1-4, wherein the design application programming interface comprises means for authoring the workflow and means for selecting one or more
of the activities to create the workflow, and where the compilation application programming interface comprises one or more of the following
means for customizing a visual appearance of the workflow,
means for compiling the workflow authored via the design application programming interface,
means for validating the workflow, and
means for serializing the workflow
6 The computerized system of claims 1-5, further comprising a type provider application programming interface for associating a type with each of the plurality of activities in the workflow, and wherein the type provider application programming interface comprises means for associating the type with each of the plurality of activities m the workflow
7 The computerized system of claims 1-6, further comprising a data structure representing the component model associated with each of the activities m the workflow, said data structure comprising
an image field storing data for visually representing the activity,
one or more author time fields storing metadata defining properties, methods, and events associated with the activity,
a senahzer field storing data for transferring the metadata stored in the author time fields to a declarative representation of the activity,
a business logic field storing software code associated with the metadata stored in the author time fields, and
an executor field storing data for executing the software code stored in the business logic field, wherein the semantic checker validates the software code stored in the business logic field
8 A computer-implemented method for modeling a workflow, said workflow including
activities, said workflow modeling a business process, said computer-implemented method
comprising
presenting a plurality of activities,
receiving a selection of the presented activities by a user, and serializing the received selection to create a persistent representation of the workflow
9 The computer-implemented method of claim 8, further comprising
providing a schedule interface for creating a schedule associated with the workflow, providing a scope interface for creating a scope associated with the schedule, providing an activity interface for selecting one or more activities, and arranging the selected activities to create the workflow within the created schedule for execution within the created scope
10 The computer-implemented method of claims 8-9, further comprising
receiving software code representing business logic from a user for association with one of the plurality of activities,
compiling the software code to create one or more binary files, and executing the created binary files to perform the workflow
11 The computer-implemented method of claims 8-10, further comprising
providing a metadata interface for receiving metadata for each of the plurality of activities from a component model associated therewith, said received metadata having semantics,
providing a validate interface for validating the received metadata by examining the semantics associated with the received metadata,
providing a code generator interface for generating software code associated with the received metadata as a function of said validating, and
providing a code compile interface for compiling the generated software code
12 The computer-implemented method of claims 8-11, further comprising
compiling the arranged activities to create an executable workflow, and executing the created workflow according to the created schedule and within the created scope
13 The computer-implemented method of claims 8-12, further comprising one or more of
the following
compiling the serialized workflow representation and software code into a single assembly containing an executable representation of the workflow,
providing the component model for association with each of the arranged activities, said component model defining properties of the arranged activities, and
translating the serialized workflow representation to another workflow language
14 The computer-implemented method of claims 8-13, further comprising
receiving a user-defined activity from the user, said user-defined activity having one
or more semantics associated therewith,
evaluating the semantics for conformance to a predefined interface requirement, and presenting the user-defined activity as one of the plurality of activities as function of
said evaluating
15 The computer-implemented method of claims 8-14, wherein presenting the plurality of
activities comprises one or more of the following
presenting the plurality of activities each having one or more properties associated therewith specifying design time, compile time, and run time behavior, and visually presenting the plurality of activities to the user
16 The computer-implemented method of claims 8-15, further comprising receiving a hierarchical organization of the selected activities from the user, and wherein the received hierarchical organization comprises one or more of the following an event-condition-action workflow, a structured workflow, and a constraint-driven workflow
17 One or more computer-readable media having computer-executable components for modeling a workflow, said workflow including activities, said workflow modeling a business process, said computer-executable components comprising
a palette component (402) for presenting a plurality of activities,
an interface component (404) for receiving, from a user, a selection and hierarchical
organization of the activities presented by the palette component (402), and
a declarative component (406) for serializing the activities received by the interface
component (404) to create a persistent representation of the workflow
18 The computer-readable media of claim 17, wherein the interface component (404)
further receives software code representing business logic from a user for association with
one of the plurality of activities, and further comprising a runtime component (408) for
compiling the workflow representation senahzed by the declarative component (406) and the software code received by the interface component (404) into a single assembly containing an executable representation of the workflow
19 The computer-readable media of claims 17-18, wherein the declarative component (406) further maps the senahzed activities to an extensible schema definition namespace for validation
20 The computer-readable media of claims 17-19, further comprising hosting the palette component (402), interface component (404), and declarative component (406) in an application program.