A PROCESSOR-BASED SYSTEM AND METHOD FOR LOCAL
CACHING OF IMAGES FOR ON-LINE CONFERENCING PROGRAMMS
BACKGROUND
The present invention relates to a processor-based system and method for
local caching of images for on-line conferencing programms and particularly, to
multiparty communications over computer networks.
In on-line meeting software, a presenter can distribute various images via a
communications network to other meeting participants such that each participant is
simultaneously viewing the same image on his or her computer. By way of example, the
image may be a slide created by presentation graphics software. Meeting participants may
then discuss a commonly displayed image by, for example, on-screen text messaging or
"chat" windows, video phones or conventional telephone conference calling.
With conventional systems, if the meeting participants wish to return to a previously
sent slide for further discussion, the image must be resent from the meeting presenter's
computer to each participant's computer. This is a time-consuming process inasmuch as
images typically comprise large amounts of data and the data must be sent over
communications channels having finite bandwidths.
WO 01/13578 discloses that a cache may be maintained on a user's
system. When the user requests data the cache is first inspected. If the
requested data is already present in the cache, then the data is served to the
user from the cache. On the other hand, if the data is not in the cache, then the
data is served from the Internet stored in the cache. However, there is no
receiving of data from a remote processor-based system related to information to
be transmitted. The cited reference simply receives requests from the user and
determines whether the information is provided. This provides no rationale to
require people who are about to transmit to you to provide information about
what is transmitted so that you can determine whether you already have it.
Thus, there is a need for a way to facilitate on-line conferences.

Accordingly, the present invention provides a processor-based system
comprising a processor and a data storage medium coupled to said processor
and storing instructions enabling said processor to set up an on-line meeting with
a remote processor-based system, receive data from the remote processor-
based system related to information to be transmitted, determine whether the
information is cached, and retrieve the cached information if the information was
cached.
The present invention also provides a method comprising setting up an
on-line meeting with a processor-based system, receiving data from the
processor-based system related to information to be transmitted, determining
whether the information is cached, and retrieving the cached information if the
information was cached.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 shows networked, processor-based systems comprising one embodiment of
the present invention;
Figure 2 is a software flow chart for one embodiment of the invention;
Figure 3 is a flow chart for another embodiment of the invention; and
Figure 4 is a flow chart for another embodiment of the invention.
Figure 5 is a flow chart for another embodiment of the invention.
Detailed Description
A network 32 includes at least two client processor-based systems 8, as shown in
Figure 1. The network 32 may be a wired or wireless local area network (LAN) in one
embodiment of the present invention. Each system 8 may include a processor 38 coupled to a
display 34 and a storage device 42. The processor-based system 8a may be used by

the presenter in an on-line meeting or conference set up between a presenter and one or
more participants. The system 8b may be used by a participant.
Both systems 8 may be personal computers in one embodiment and the storage 42
may be, for example, a magnetic media disk drive with associated disk controllers or
5 solid-state memory such as random access memory (RAM). The system 8b storage 42
'may store software 40 for enabling the processor 38 to participate in a network
presentation as well as the data 30 to be presented. The system 8a storage 42 may store
software 50 for implementing a network presentation.
The software 40 may operate as part of or work with on-line conferencing
10 software. An example of on-line conferencing software is NetMeeting software from
Microsoft Corporation, Redmond, Washington.
An on-line meeting may be set up between a presenter system 8a and one or more
participant systems 8b by establishing communications over a network 32, as indicated at
block 10 of Figure 2. The presenter's system 8a may send data to each of the participant
15 systems 8b. The shared data may be, for example, a series of images or frames. The
presenter's system 8a may send each image when the presenter desires to change the
image displayed for viewing by the participants.
The presenter may have created the images with presentation graphics software
and the images may comprise slides. Each slide may have a unique identifier that may be,
20 for example, a file attribute of the data comprising the image.
During the course of the on-line meeting, the presenter's system 8a may send data
relating to a slide to participant systems 8b, as indicated at block 14. As shown at
diamond 18, a participant's system 8b may determine, for example by testing the slide
identifier, whether the slide being sent by the presenter's system 8a is a new slide or a
25 previously-sent slide. Multitasking techniques may be employed by a participant's system
8a to compare the identifier with the identifiers of cached images while the session is still
in progress.
If the slide is a previously-sent slide, it may be available in a local cache of slides
and may be retrieved from the cache, as indicated at block 22. The cached slide may be
30 displayed, as indicated at block 26, on the participant's processor-based system 8b.

If the slide is in the local cache, the transmitted image data may be directed to a
"bit bucket" while the cached slide is retrieved and displayed as indicated at blocks 22 and
26, respectively. A bit bucket is an imaging location into which data can be discarded.
If, however, the slide is nor in the cache, the slide may be downloaded from the
5 presenter's system 8a over the network 32, as indicated at block 20, and subsequently
cached and displayed, as indicated at blocks 24 and 26, respectively. In this way,
participants who join the meeting late may download a slide previously sent to other
participants without delaying the image viewing by the earlier-joining participants whose
systems may have the slide in their local caches.
10 Inasmuch as data can typically be retrieved from a local cache more quickly than it
can be downloaded via a network 32, participants in an on-line meeting can save time
whenever the presenter returns to a previously-sent slide for discussion that is already
available in a participant's system 8b.
If the meeting is concluded, as indicated at the right branch of diamond 28, the
15 participant system 8b may disconnect from the session as indicated at block 30. The
meeting may be over when an indicating signal is sent from the system 8a to the system 8b
in one embodiment. If the meeting is not over, as indicated by the lower branch of
diamond 28, the participant's system 8b may query the presenter to determine whether the
presenter has changed his or her system to edit mode, as indicated at diamond 12.
2D Graphics generating programs may have multiple modes of operation. For
example, a software package for presentation graphics may have an editing mode wherein
slides are created and modified and a presentation mode or "slide show" mode wherein a
predetermined sequence of slides is displayed seriatim.
The presenter may desire to edit the presentation graphics during the course of an
25 on-line meeting. In such a situation, the presenter may change the state of the system 8a
from a presentation mode to an editing mode. If the presenter alters one or more images
on his or her system, one or more images which may have been cached by the participants'
systems may no longer correspond to the images stored by the presenter's system 8a even
though the images may have the same identifier. In such an instance, a participant system
30 8b local cache is "stale" and should be "flushed", as indicated at block 19 - i.e., cleared

from the data storage sub-system of a participant's system as though no images were
cached.
The presenter's system 8a may broadcast a message or code that indicates to all
participant systems 8b that the presenter has switched his or her system to editing mode.
5 In response, each participant's system 8b local cache may be flushed, as indicated at block
19. Alternatively, each participant system 8b may query the presenter's system 8a
regarding its mode, as indicated at diamond 12. If the presenter's system 8a responds that
it is in edit mode, the participant's system 8b may flush its local cache, as indicated at
block 19. In yet another alternative, the presenter's system 8a may indicate which image
10 or images have been altered and, in response, the participant's system 8b may flush only
those images from its local cache.
In this way, a meeting participant's system 8b may build a local cache of slides
during the course of an on-line meeting as the meeting presenter's system 8a sends
individual slides, seriatim. During a meeting, because a participant's system 8b is able to
15 retrieve previously-sent slides from a local cache, the images may be displayed more
quickly than if the image data is again downloaded from a network 32.
In another embodiment, an on-line meeting presenter's system may send a slide
identifier (but initially not image data) to meeting participant system 8b, as indicated at
block 15 of Figure 3. The presenter system 8a may then wait for a request from a
20 participant system 8b for the image data comprising the slide.
As indicated at block 17 of Figure 3, a meeting participant system 8b may
determine from the slide identifier whether the slide exists in its local cache. If the slide is
found in the local cache, it may be retrieved from the cache 22 and displayed, as indicated
at blocks 22 and 26, respectively.
25 If, however, the image data comprising the slide is not found in the local cache, as
indicated at the right branch of diamond 17, the participant system 8b may request the slide from the presenter system 8a, as indicated at block 21. The presenter system 8a may,
in response, send the requested slide, as indicated at block 16, which data may then be
stored by the participant system 8b in its local cache and displayed, as indicated at blocks
30 24 and 26, respectively.

In this embodiment, the presenter system 8a need not send the image data
comprising the slide if all participant systems 8b already have the slide in their local
caches - i.e.. if no participant system 8b requests a download of the image data. In this
way, both time and network resources may be conserved.
5 In yet another embodiment, cache-participants may receive a download of a slide
during the course of an on-line meeting and subsequently determine whether a cached
version differs from the downloaded version. In the meantime, the cached version may be
displayed. The presenter's system 8a may send data relating to a slide to participant
systems 8b, as indicated at block 14 of Figure 5. A participant's system 8b may extract a
10 slide identifier from this data as shown at block 15a. As shown at diamond 17, a
participant's system 8b may then determine, for example by testing the slide identifier,
whether the slide being sent by the presenter's system 8a has the same identifier as a
previously-sent slide. Multitasking techniques may be employed by a participant's system
8a to compare the identifier with the identifiers of cached images while the session is still
15 in progress.
If the slide identifier corresponds with that of a previously-sent slide, it may be
available in a local cache of slides and may be retrieved from the cache, as indicated at
block 22. The cached slide may be displayed, as indicated at block 26a, on the
participant's processor-based system 8b along with a warning to the viewer that the slide
20 may not correspond with that of the presenter's system.
As indicated at block 20, the download of image data may be completed by the
participant's system. As indicated at diamond 23, the just-downloaded image data may
then be compared to the cached image data having the same slide identifier to determine
whether there has been any change in the data. If no change is detected, the warning on
25 the display may be removed as indicated at block 26c. If, however, a change is found, the
just-downloaded data may be stored in the cache replacing the previously stored data
having the same identifier, as indicated at block 24a. The displayed image may then be
updated using the new data and the display warning removed as indicated at blocks 26b
and 26c, respectively. If the changes in the image data are minimal, display techniques
30 may be employed to smoothly "morph" the image from the previous version to the more
recent one.

If, however, the slide is not in the cache as indicated by the left branch of diamond
17, the slide may be downloaded from the presenter's system Sa over the network 32, as
indicated at block 20a, and subsequently cached and displayed, as indicated at blocks 24
and 26, respectively.
5 In this way, the speed of a cache-based system may be realized whenever the
meeting participants return to a previously sent slide even if the image must subsequently
be modified due to a change in the image by the presenter.
Referring to Figure 4, the software 50 on the presenter system 8a may implement
the caching protocol in conjunction with the participant systems 8b. Initially, the presenter
10 system 8a establishes the network meeting as indicated in block 52. Information may be
sent to the participants concerning each slide as indicated in block 54. In some
embodiments, this may include the initial download of a portion of the slide. In other
embodiments, only an identifier for the slide may be provided. If only an identifier is
provided, then the information is not sent until the participant indicates that it actually
15 wants the download. If only a portion of the slide is provided, the same protocol may be
utilized or, the information may be transmitted even if the participant determines that it
will not receive the information.
If the download is requested as determined in diamond 56, the data may be sent as
indicated in diamond 58.
20 In another embodiment, the network 32 may be the Internet. In such case, the
systems 8 may communicate and send slides or other data over the Internet.
While the present invention has been described with respect to a limited number of
embodiments, those skilled in the art will appreciate numerous modifications and
variations therefrom. It is intended that the appended claims cover all such modifications
25 and variations as fall within the true spirit and scope of this present invention.

WHAT IS CLAIMED IS :
1. A processor-based system comprising :
a processor ; and
a data storage medium coupled to said processor and storing
instructions enabling said processor to set up an on-line meeting with a
remote processor-based system, receive data from the remote processor-
based system related to information to be transmitted, determine whether the
information is cached, and retrieve the cached information if the information
was cached.
2. A processor-based system as claimed in claim 1 wherein the data
storage medium stores instructions enabling the processor to receive an
image identifier.
3. A processor-based system as claimed in claim 2 wherein the data
storage medium stores instructions enabling the processor to determine
whether the image identifier identifies cached information.
4. A processor-based system as claimed in claim 3 wherein the data
storage medium stores instructions enabling the processor to receive a
portion of a downloaded image.
5. A processor-based system as claimed in claim 1 wherein the data
storage medium stores instructions enabling the processor to determine a
state of the remote processor-based system and flush cached information
depending on the state of the remote processor-based system.
6. A processor-based system as claimed in claim 5 wherein the data
storage medium stores instructions enabling the processor to determine
whether the remote processor-based system is in a state which allows images
to be altered and if so to flush the cached information.

7. A processor-based system as claimed in claim 1 wherein the data
storage medium stores instructions enabling the processor to download
information for the remote processor-based system if the information is not
cached.
8. A processor-based system as claimed in claim 7 wherein the data
storage medium stores instructions enabling the processor to cache the
downloaded information.
9. A processor-based system as claimed in claim 8 wherein the data
storage medium stores instructions enabling the processor to associate the
cached information with an identifier.
10. A processor-based system as claimed in claim 9 wherein the data
storage medium stores instructions enabling the processor to associate the
cached information with an identifier provided with said data.
11. A method comprising :
setting up an on-line meeting with a processor-based system ;
receiving data from the processor-based system related to information
to be transmitted ;
determining whether the information is cached ; and
retrieving the cached information if the information was cached.
12. The method as claimed in claim 11 comprising determining a state of
the processor-based system and flushing cached information depending on
the state of the processor-based system.
13. The method as claimed in claim 12 comprising determining whether
the processor-based system is in a state which allows images to be altered
and if so flushing the cached information.

14. The method as claimed in claim 11 comprising flushing cached
information in response to data received from the processor-based system.

Networked systems (8a, 8b) may participate in data sharing sessions
in which previously transmitted data is cached. When a system (8a, 8b)
learns that it is about to receive data that was cached previously, the system
(8a, 8b) can recall the cached data instead of receiving a new data download
A processor-based system (8a, 8b) comprises a processor (38) and a
data storage medium (42) coupled to said processor (38) and storing
instructions enabling said processor (38) to set up an on-line meeting with a
remote processor-based system, receive data from the remote processor-
based system related to information to be transmitted, determine whether the
information is cached, and retrieve the cached information if the information
was cached.