A METHOD AND SYSTEM FOR TIME SHIFTING ENHANCED
TELEVISION TRIGGERS
Background of the Invention
This invention relates to a method and system for time shifting enhanced
television triggers and a system therefor, and generally to enhanced television
broadcasts including analog and digital broadcasts.
Enhanced television programming enables television programming, in
analog or digital form, to be accompanied by additional content. In some
embodiments, the additional content may be in the form of Internet-based
content. With enhanced television technology, content creators (e.g.,
broadcasters) may transmit hypertext markup language (HTML) data along with
the traditional television signals. Viewers may intelet with the television
broadcast via the Internet.
For example, enhanced* features may be displyed on a television
screen that enable the viewer to access the network's web site for related
programming information. The related programing information may be
additional advertising or additional details that are not readily incorporated into
the television program itself, as examples. Thus, the user may selectively
access additional information through an Internet connection.
A variety of standards exist for enhanced television broadcasts
including the Advanced Television Enhancement Forum's (ATVEF) Enhanced
Content Specification, Version 1.1, Revision 26, 1998-1999 (hereinafter
referred to as the ATVEF specification). The ATVEF specification provides
standards for the transmission and processing of triggers, resources and
announcements together with television content to produce a digital or analog
enhanced television transmission.
In order to announce the availability of interactive television resources, a trigger
may be utilized. Announcements announce programming currently available to
the receiver. A resource is a television enhancement or web
content displayable in conjunction with a television
broadcast as an enhanced or interactive program.
According to the ATVEF specification, there are two
basic transport types, called transport type A and transport
type B. In transport type A, the resource is accessed over
the Internet and in transport type B, the resource is
transmitted with the television content.
Triggers may include a Uniform Resource Locator and may
optionally also include a human readable name, an expiration
date and a script. Triggers that include a name attribute
may be utilized to initiate enhancements either
automatically or with user confirmation. The initial top-
level page for an enhancement is indicated by a Uniform
Resource Locator in the trigger. The script attribute
provides a script fragment to execute within the context of
the page containing a trigger receiver object
The expires attribute provides a expiration time, after
which the link is no longer valid. The expires attribute
may be in the form [expires: 19971223] according to one
example provided in the ATVEF specification.
In some cases, the link tc the resource provided by the
trigger may be caused to expire after a period of time.
This may create problems. For example, in some situations,
the enhanced television content may be retransmitted by a
local affiliate or so-called franchise network operating
center (FNOC). The FNOC may receive the broadcast and then
retransmit it at an appropriate time, for example given the
FNOC,s local time zone. As a result, the expiration time
may come and go before the broadcast is ever even
transmitted. In such case, a user may be unable to activate
the link to obtain the resource.
Similarly, digital recording technology may be available to enable the
user to actually record an enhanced broadcast. The user may subsequently
attempt to replay the recorded broadcast and may be unable to activate the
links to the resource because the links have expired.
Thus, there is a need to enable time shifted enhanced television content
to be used effectively in a variety of circumstances.
Accordingly, the present invention provides a method for time shifting
enhanced television triggers, said method comprising the steps of : receiving
an enhanced television transmission including a trigger that points to a
resource and has an expires attribute indicating a trigger expiration time ; and
enabling the resource to be accessed after the trigger expiration time.
This invention also provides a system for time shifting enhanced
television triggers, said system comprising : a process-based device ; and a
storage coupled to said processor-based device storing instructions that
enable said processor-based device to receive an enhanced television
transmission including a trigger that points to a resource and has an expires
attribute indicating a trigger expiration time and enable the resource to be
accessed after the trigger expiration time.
Brief Description of the Accompanying Drawings
Figure 1 is a schematic depiction of one embodiment of the present
invention ;
Figure 2 is a flow chart for software in accordance with the embodiment
shown in Figure 1 ;
Figure 3 is a schematic depiction of another embodiment of the present
invention ;
Figure 4 is a flow chart for software utilized in accordance with the
embodiment shown in Figure 3 ;
Figure 5 is a functional block diagram illustrating an embodiment of
the invention ;
Figure 6 is a flow diagram showing operation of an illustrative type of
trigger inserter unit that can be used with the embodiment shown in Figure 5 ;
Figure 7 is a flow diagram showing operation of an illustrative type of
stream simulator unit that can be used with the embodiment shown in Figure 5;
Figure 8 is a flow diagram showing operation of an illustrative type of
proxy that can be used with the embodiment shown in Figure 5 ; and
Figure 9 is a flow chart for software in accordance with another
embodiment of the present invention.
Detailed Description
Referring to Figure 1, an enhanced television delivery
system 10 may include a broadcast head end or server 12.
The head end or server 12 may provide the television content
such as a television program and the enhanced content or at
least a reference to the enhanced content. The enhanced
television broadcast is transmitted from the head end 12 to
a plurality of receivers 16 (although only the receivers 16a
and 16b are. shown in Figure 1). The enhanced content may be
transported over a transport 14 which may be a cable, a
satellite connection or a conventional television broadcast.
The enhanced content may be in analog or digital format.
Each receiver 16 may include a storage 17 that stores
software 18. The receiver 16 may be a processor-based
system. As examples, the receiver 16 may be a desktop
computer, a laptop computer, a handheld computer, a set-top
box or other processor-based appliance with a suitable
connection to receive the enhanced content over a transport.
The software 18 enables the enhanced content to be time
shifted despite the presence of triggers with expiration
times.
Referring to Figure 2, the software 18 handles the
situation where a receiver 16 is utilized to digitally
record an enhanced television broadcast. The user may
record not only the programming, but also the accompanying
triggers. A trigger may be in the form of a Uniform
Resource Locator (URL) used to access enhanced content over
the Internet or may be a reference to a local storage
location of a referenced resource.
Of course, if the trigger has an expiration time, the
user may attempt to access the resource via the trigger long
after the trigger has expired. In such case, the user may
be unable to access the trigger even in the situation where
the resource is actually still accessible.
Referring to Figure 2, the software 18 initially
obtains the local time as indicated in block 20. The local
time may be stored as indicated in block 22. The local time
may then be converted into Universal Coordinated Time (UTC),
as indicated in block 24, and stored as indicated at 26.
The trigger expiration time may be extracted from the
video stream as indicated at 30. The current local time
(LocalT) is then subtracted from the trigger expiration time
as indicated in block 28. The result is a delta time as
indicated at 32. If the delta time is negative, the trigger
has already expired and it may simply be discarded as
indicated in block 31.
Otherwise, as determined in diamond 34, if the delta
time is zero or positive, the expires attribute may be
discarded as indicated in block 38. The trigger may then be
recorded with the other enhanced television content without
a expires attribute. In effect then, a trigger with an
expires attribute is converted into a format in which the
expires attribute is removed. The absence of an expires
attribute is permissible under the ATVEF specification.
The resulting trigger is then capable of being
exercised at any time. If the resource is stored locally
(i.e. via a Type B transport), that resource can then be
acquired anytime the trigger is selected. If the resource
is accessed externally (i.e. via a Type A transport), the
resource may not always be active. In such case, the
trigger may not be capable of accessing the remote resource.
However, if desired, the remotely accessible resource
may be accessed upon acquisition of the trigger and the
resource may thereafter be stored locally for subsequent
local access. Alternatively, the trigger's Uniform Resource
Locator may be modified to a local storage address to access
the locally stored resource.
Referring to Figure 5, a system 110, in accordance with
one embodiment for recording analog enhanced television
broadcasts includes a recording component or "recorder" 112,
and a playback component or "player" 114. According to one
embodiment of the invention, the recorder 112 stores
Transport Type B streams (and can also store Transport Type
A streams), while the player 114 can transform and play the
stored streams as Transport Type A streams.
An enhanced television Transport Type B transmission
includes a trigger stream 116, an audio/video stream 118, a
resource stream 120, and an announcement stream (not shown).
The audio/video stream 118 may be a National Television
Standards Committee (NTSC) signal. In operation,
announcements are sent before or during a television program
to a well-known Internet Protocol (IP) address and port
number to announce the availability of enhancements. A
receiver tunes in to this IP address/port and receives
information about how to receive trigger and resource
information, where the trigger typically includes a URL that
points to a location of the resource.
If resources in the resource stream 12 0 are extracted
by a resource listener 122, such resources are typically
stored in a storage media 12 4, which may be a cache, for
example. The storage media 124 may also be a hard disk,
floppy disk, digital versatile disk, random access memory
(RAM), compact disk, or other suitable machine-readable
storage medium. The resource listener 122 may be programmed
to reject duplicate or outdated resources, such that only
the appropriate resources are stored in the storage media
124.
When the resources are stored in the storage media 124,
the trigger(s) corresponding to those stored resources
typically include a local identifier URL (e.g., a lid: URL),
meaning that the resources were delivered using a one-way
broadcast and are not available on-demand. As such,
Transport Type B is used for a true broadcast of both
resource data and triggers and can run without an Internet
connection. An optional Internet connection can provide a
return path if the triggers point (e.g., by using http: or
ftp: URLs) to resources that are available on the Internet
(e.g., for e-commerce or web browsing).
Transport Type A involves the delivery of triggers
along with the audio/visual stream 118. That is, existing
Transport Type A transmissions often transmit triggers on
the vertical blanking interval (VBI) of the NTSC video
signal. Transport Type A transmissions may not transmit a
resource stream 120 or an announcement stream. Hence,
Transport Type A systems usually use two-way Internet
connections to fetch resources using http:.
The system 110 includes a trigger inserter unit 126 for
the recorder 112, and a stream simulator unit 128 (which can
be likened to a Transport Type A stream simulator) and a
proxy unit 130 for the player 114. The end result is that
one or more resources 132 may be provided to a receiver unit
16, from the storage media 124, without having to
unnecessarily retrieve the resources 132 from the Internet.
Furthermore, using the trigger inserter unit 12 6 to insert
triggers into the video signals (e.g. into the VBI) of the
audio/video stream 118 provides synchronization between the
trigger stream 116 and the audio/video stream 118 that is
not present in conventional Transport Type B systems.
Operation of an embodiment of the trigger inserter unit
12 6 of the recorder 112 is illustrated in a flow diagram in

Figure 6. The trigger inserter unit 126 can be embodied in
software, hardware, or a combination of both, and uses data
from the trigger stream 116 and data from the audio/video
stream 118 as inputs.
At a block 136, the trigger inserter unit 126 first
determines if there is a trigger available in the received
broadcast. If the received broadcast is a Transport Type A
transmission, such triggers, if any, may be in the VBI of
the audio/video stream 118 for examples. The triggers are
extracted and evaluated for validity as part of the
receiving process. If the triggers are valid, the trigger
inserter unit 12 6 stores the data from the audio/video
stream 118 (and its associated valid triggers) into the
storage media 124 at block 140.
If a Transport Type B transmission is present, then the
trigger inserter unit 126 detects the availability of valid
triggers from the trigger stream 116 at block 136. At block
138, the trigger inserter unit 12 6 combines the trigger data
with the audio/visual data. More specifically, according to
an embodiment of the invention, the trigger inserter unit
126 inserts triggers into the VBI of the audio/visual stream
118. In this manner, the Transport Type B stream is
"transformed" into Transport Type A stream prior to storage
into the storage medium 124 at the block 14 0. Accordingly,
by inserting the triggers into the VBI, as the trigger
stream 116 and the audio/visual stream 118 are received, the
triggers are synchronized in time with the audio/visual data
by presenting the triggers along with their corresponding
video frames.
At block 140, the trigger inserter unit 126 stores the
data into the storage media 124 using a suitable type of
audio/video streaming and storage format. Formats such as
RealVideo™/RealAudioTM, Flash™, QuickTime™, Audio Video
Interleaved (AVI), Motion Pictures Experts Group (MPEG),
DVD, etc. may be used.
The trigger may include URLs pointing to locations of
resources. These URLs may be in the form of lid: URLs
pointing to the storage media 124 if the corresponding
resources were extracted from the resource listener 122 and
subsequently stored in the storage media 12 4. The URLs in
the trigger may also be http: URLs if the corresponding
resource is available both from the storage medium 124 and
from the Internet. Similarly, other URL schemes, such as
ftp:, may be used by the triggers to denote the location of
resources available from the storage media 12 4 or from the
Internet.
In one embodiment, the resource listener 122 extracts
resources from the resource stream 120, regardless of its
specific URL, and then stores these resources in the storage
media 12 4. The manner of retrieving stored resources from
the storage media 12 4, rather than from an external Internet
source, is described in further detail below with respect to
the proxy unit 130.
Figure 7 shows an embodiment of the stream simulator
unit 128 that can be used by the player 114. The stream
simulator unit 128 may be embodied in software, hardware, or
a combination of both. In operation, the stream simulator
unit 12 8 reads, from the storage media 12 4, the stored
audio/video stream 118 and the trigger stream 116 at a block
142. In some embodiments, the stream simulator unit 128 may
format the resulting stream at a block 14 4, in order to make
the resulting stream compatible with the format used by the
applicable presentation/display application software. For
example, if Microsoft Window's DirectShowTM is used as the
presentation software, then the stream simulator unit 128,
at the block 144, can format the resulting stream into the
DirectShowTM architecture using libraries in the Windows
environment.
Next, the stream simulator unit 12 8 provides the
simulated Transport Type A stream to the receiver 16. As an
example, the receiver 16 may comprise a conventional
television set as the display unit 14 8 and having the
enhanced television module 14 6 as a separate unit coupled to
the television set. The enhanced television module 146 may
have the capability to receive enhanced television broadcast
data, display/announce the enhanced television features to
the user, and then provide the user with interfaces to allow
the user to input information (e.g., to interact) with the
enhanced broadcast.
Operation of the player 114 using the receiver 16, the
stream simulator unit 128, and the proxy unit 130 is shown
in Figure 8 in accordance with one embodiment of the
invention. The proxy unit 130 may be thought of as an
"http: proxy" in that it intervenes in the retrieval of
resources 132 having http: URLs. The proxy unit 130 can
also be made to intervene and retrieve resources 132 having
lid: URLs or other protocol resources, such as a resource
having an ftp: URL. That is, the proxy unit 130, in one
embodiment, may comprise a thin/simple agent that can
reroute a resource request and retrieve the requested
resource from a local cache (e.g., from the storage media
124) if available, but relinquishes or invokes a normal
http: handler to perform the retrieval if the requested
resource is not in the local cache {and assuming that an
uplink or back channel to the Internet is available).
The proxy unit 130 may be embodied in software,
hardware, or a combination of both. In one embodiment, the
proxy unit 130 can comprise a set of software communication

instructions or settings in a registry of an operating
system of a PC, for example.
In one example, when the receiver 16 receives an
enhanced television broadcast, in a simulated Transport Type
A stream format having triggers inserted in the VBI, the
user can request the resources 132 or the receiver 16 can
automatically request the resources 132. If the receiver 16
is Transport Type A-enabled, the requested resources 132 are
retrieved externally from the Internet. Therefore, at a
block 150 in Figure 8, the receiver 16 sends a URL request
for the resource 132 using http: protocols. If the trigger
included a lid: URL, rather than an http: URL, then the
receiver 16 and/or proxy unit 130 can retrieve the resource
132 directly from the storage media 124, which may be a
local cache.
At diamond 152, the proxy unit 130 intercepts the http:
request from the receiver unit 134 and determines if the
resource 132 is in the storage media 124. If it finds the
resource 132 in the storage media 124, then the resource 132
is retrieved from the storage media 124, as indicated at
block 154, and is provided to the receiver 16 for display
and/or other use by the receiver 16. As indicated at
diamond 152, the proxy unit 130 may retrieve resources 132
having lid: URLs from the storage media 124, as well as
resources 132 having http: or ftp: URLs from the storage
media 124, if the resources 32 are stored there, or
externally from the Internet.
If the proxy unit 130 does not find the requested
resource 132 in the storage media 124, then at a block 156,
the proxy unit 134 may attempt to retrieve the resource 132
from the network (e.g., from the Internet). If the
retrieval is unsuccessful as determined at 158, then a
failure message is sent to the receiver 16. In response,

the receiver 16 may cause the proxy unit 130 to try again,
or the receiver 16 may display a message to the user on the
display unit 148 to notify the user of the unavailability of
the resource 132 or other appropriate response.
If the resource 132 is successfully retrieved by the
proxy unit 130, then the retrieved resource 132 can be
stored in the storage media 124, as indicated at block 160,
and then subsequently provided to the receiver 16, thereby
providing the user with enhanced television content and
features.
Embodiments of the invention may transform Transport
Type B streams into a simulated Transport Type A stream by
inserting triggers into the video stream. The recorder 112
stores resources and the transformed stream in the storage
media 124. During playback, the player 114 may read the
triggers in the stored simulated Transport Type A stream
from the storage media 124 and use the proxy unit 130 to
retrieve requested resources from the storage media 124 or
externally from the Internet, if the resource is not already
stored. As such, Transport Type B transmissions appear like
and are treated like Transport Type A transmissions by the
receiver unit 134.
Referring next to Figure 3, an embodiment with a
regional affiliate or FNOC 82 includes a broadcast head end
12 and transport 14 as described previously. The FNOCs 82a
and 82b receive the enhanced television programming over the
transport 14 and then provide the programming to local
receivers 16. The local receivers 16a and 16b may receive
the broadcast over still another transport (not shown).
Each FNOC 82 may include a storage 8 4 that stores
software 50. The FNOCs 82 may include a processor-based
system that is capable of executing the software 50 stored
on the storage 84.

If the FNOC rebroadcasts the enhanced broadcast at a
later time than was originally intended, an issue arises
with respect to trigger expiration. For example programming
originating in one time zone may be provided to a FNOC 82 in
another time zone. The FNOC 82 may determine that it is
most appropriate to time shift the programming to an
appropriate local time zone, time slot for rebroadcast.
However, in some cases, the triggers may be expired by the
time the material is actually retransmitted.
The software 50 accounts for this potential
transmission time shifting by the FNOC and adjusts the
expires attribute accordingly. Referring to Figure 4, the
software 50 begins by obtaining the FNOCs enhancement start
time or the scheduled time for the program to start (StartT)
as indicated in block 52. The enhancement start time
indicated in block 54, is converted to UTC at 5 6 and as
indicated at 58.
The trigger expire time (TriggerT) is extracted from
the enhanced television stream as indicated at 62. The
enhancement start time (StartT) is then subtracted from the
trigger expire time (TriggerT) as indicated in block 60.
This results in a delta time (DeltaT) as indicated at 64.
A check at diamond 6 6 determines whether the delta time
is greater than or equal to zero. If not, the trigger is
discarded as indicated in block 68.
Otherwise, a retransmission time equal to the
retransmission start time plus the delta time is utilized
(block 70) as the new expires attribute in the trigger. The
retransmission start time or time that the FNOC will
rebroadcast the enhanced programming in local time is
acquired as indicated at 72, converted to UTC as indicated
in block 7 4 and stored as a retransmission start time as
indicated at 76. Thus, the retransmission start time as

determined by the FNOC is then added no the delta time at
block 70, to create a new trigger expires attribute as
indicated at 78. This attribute is saved as indicated at
block 80.
As a result, the expiration time may be executed as
originally intended at the head end. That is, the
expiration time may be extended in accordance with local
time to a predetermined amount of time after the initial
broadcast. This effectuates the original intent of the
expires attribute in the original enhanced television
broadcast.
In the case of rebroadcasting data received via a Type
B transport, the resource may be locally accessible and the
handling of the triggers may be in accordance with the above
description. However, in the case where the FNOC receives a
Type A transport, simply adjusting the expires attribute
without more may result in the situation where the resources
may not be accessible because the web site addressed through
the trigger may no longer be operable.
This problem may be handled in at least two different
ways. Under one approach, the FNOC may automatically access
the web site through the trigger's URL and download the
content therein. The FNOC may then transmit the resource
with the other enhanced content via a Type B transport.
Alternatively, the FNOC may translate the trigger's URL to a
mirror web site maintained by the FNOC. That is, the FNOC
may acquire the content via the URL referenced by the
trigger, and copy it over to the FNOCs own web site. The
FNOC may then automatically translate the URL in the trigger
to a new URL to enable access to the FNOC controlled web
site. In this way, the FNOC can control the availability of
the resource while maintaining a type A transport.
Referring to Figure 9, software 170 may be stored and
utilized in conjunction with the software 50. Initially,
the content is received over the transport as indicated in
block 172. A check at diamond 174 determines whether the
content is in the type A transport format. If not, the flow
ends, and the triggers can be handled readily.
Conversely, if a type A transport is utilized, a check
at diamond 17 6 determines whether a flag is set. In one
embodiment of the present invention, the FNOC can set or
unset a flag to select whether to convert the type A
transport to a type B transport with a locally stored
resource or to simply transition the data from the
broadcaster's web site to the FNOCs web site. Thus, the
FNOC can decide whether to use its own web site or to access
the data from the broadcaster's web site and to transmit the
data to the receiver 16.
If the flag is not set, the data may be converted to a
type B transport, storing the accessed resource locally as
indicated in block 180. That is, the FNOC accesses the
resource from the broadcaster's web site, and then transmits
the resource with the other content to the receiver 16.
Conversely, if the flag is set, the FNOC translates the
broadcaster's URL to point to the FNOC's mirror site as
indicated in block 17 8.
In some embodiments of the present invention, time
shifted transmissions or playback of enhanced television
content may be accommodated despite the use of expires
attributes in associated triggers. In this way, the expires
attribute may be utilized but the system may not become
unduly burdened by the expires attribute.
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 and variations as fall
within the true spirit and scope of this present invention.
What is claimed is:

WHAT IS CLAIMED IS :
1. A method for time shifting enhanced television triggers, said method
comprising the steps of:
receiving an enhanced television transmission including a trigger that
points to a resource and has an expires attribute indicating a trigger expiration
time ; and
enabling the resource to be accessed after the trigger expiration time.
2. The method as claimed in claim 1, comprising rebroadcasting the
enhanced television transmission.
3. The method as claimed in claim 1, comprising differencing the current
time and the trigger expiration time.
4. The method as claimed in claim 3, comprising determining whether
the trigger time is greater than the current time and if not, discarding the
trigger.
5. The method as claimed in claim 2, comprising determining whether
the trigger time is greater than the enhancement start time and if so,
retransmitting the trigger with a trigger expiration time equal to the time when
the enhanced television transmission will be rebroadcast plus the difference
between the trigger time and the enhancement start time.
6. The method as claimed in claim 1, comprising recording said enhanced
television transmission for subsequent replay.
7. The method as claimed in claim 6, comprising differencing the current
time and the trigger expiration time.
8. The method as claimed in claim 7, comprising determining whether the
difference is greater than zero.
9. The method as claimed in claim 8, wherein if the difference is not
greater than zero, discarding the trigger before recording said enhanced
television transmission.
10. The method as claimed in claim 8, wherein if the difference is greater
than zero, discarding the trigger expiration time and recording the trigger.
11. The method as claimed in claim 1, comprising receiving an enhanced
television transmission having a trigger that refers to a remote resource,
accessing said remote resource and storing said remote resource.
12. A system for time shifting enhanced television triggers, said system
comprising :
a process-based device ; and
a storage coupled to said processor-based device storing instructions
that enable said processor-based device to receive an enhanced television
transmission including a trigger that points to a resource and has an expires
attribute indicating a trigger expiration time and enable the resource to be
accessed after the trigger expiration time.
13. The system as claimed in claim 12, wherein said system is an enhanced
television receiver with a broadcast recording device.
14. The system as claimed in claim 12, wherein said system is an enhanced
television rebroadcast system.
15. The system as claimed in claim 14, wherein said storage stores
instructions that difference the trigger expiration time and the enhancement
start time.

16. The system as claimed in claim 15, wherein the trigger is discarded if
the trigger has expired.
17. The system as claimed in claim 12, wherein said storage stores
instructions that enable said system to receive enhanced television
transmission having a trigger that refers to a remote resource, access said
remote resource and store said remote resource.
18. The system as claimed in claim 17, wherein said storage stores
instructions that enable said system to convert a type A transmission to a type
B transmission.
19. The System as claimed in claim 17, wherein said system makes said
resource available at a new location and translates said trigger to point to said
new location.
20. A method for time shifting enhanced television triggers, substantially as
herein described, particularly with reference to and as illustrated in the
accompanying drawings.
21. A system for time shifting enhanced television triggers, substantially as
herein described, particularly with reference to and as illustrated in the
accompanying drawings.
A method for time shifting enhanced television triggers, comprises the
steps of: receiving an enhanced television transmission including a trigger that
points to a resource and has an expires attribute indicating a trigger expiration
time ; and, enabling the resource to be accessed after the trigger expiration
time.
A system for time shifting enhanced television triggers, comprises : a
process-based device (16) ; and, a storage (18) coupled to said processor-
based device storing instructions that enable said processor-based device to
receive an enhanced television transmission including a trigger that points to a
resource and has an expires attribute indicating a trigger expiration time and
enable the resource to be accessed after the trigger expiration time.