Trigger Types

[This is preliminary documentation and subject to change.] 

To write trigger events, use the syntax appropriate for the trigger you want to write. There are two categories of triggers: reserved triggers, which are built into Microsoft Broadcast Architecture, and user triggers, which the enhancements producer can create in the event that the reserved triggers are not adequate to support enhancements created for the interactive show.

A trigger is an event statement in the stream script describing an event scheduled to take place in a HTML (Hypertext Markup Language) page—known in the stream script as an asset—at a certain point in time in an interactive show. Triggers are executed by the Enhancement control, which carries out the instructions of the triggers.

Each type of trigger sent to the Enhancement control has a specific format associated with it. The basic trigger format is a string that contains two parts, a key or numerical identifier, and the trigger data. The key is separated from the data by white space, typically a space or tab character. Optionally, a trigger string can also have keywords at the beginning and end of the string, and can also have a timestamp located prior to the trigger and Key parameters. Like other parameters in a trigger string, these are delimited from other parameters with white space.

The syntax of a trigger is as follows:

keyword1 timestamp trigger (Key "TriggerData") keyword2 ;

where

keyword1

is an optional parameter, such as now or before. For more information, see Keywords Syntax.

timestamp

is an optional parameter indicating, in an acceptable time format, the point in the show when the event will take place. For more information, see Time Syntax.

Key

is the trigger identifier number that specifies what kind of a trigger it is.

TriggerData

is information describing the file or other show element that the trigger is acting upon.

keyword2

is an optional parameter, such as only, or repeat x until y. For more information, see Keywords Syntax.

For example, the following string might be specified in a NavBase trigger:

 00:00:46.00	trigger (2 "http://www.microsoft.com/default.htm") repeat 00:01:00.00 until 00:30:00.00 ;

List of Triggers

The Enhancement Stream language, along with the Microsoft Enhancement Author and the enhanced video controls, supports several types of triggers for different purposes. With the exception of user triggers, all the triggers in the following list are reserved triggers. The number that precedes the trigger name is the numeric reference for that trigger, and is the designation you use in a stream script when you write a trigger statement.

1   Data.   Receives data using the transfer protocol you specify, either compressed cabinet (CAB) or File Transfer Services (FTS).

2   Nav.   Displays the specified page either in the top-level viewing area or in a specific target portion of the viewing area, as defined by the following tags: <FRAME>, <IFRAME>, <SPAN>, <DIV>.

4   Script.   Executes a script that is embedded in the base page of the interactive show.

5   TVCrossover.   Runs the specified Microsoft JScript script.

6 - 999.   Reserved.   Key values reserved for future trigger functionality.

1000 and up   User-Defined triggers.   Execute user-defined trigger events.