3 Message Patterns

3.1 Message Pattern Attributes

3.2 Scope Attributes

Scoping to a Session Only

Scoping to a File Only

Scoping to a File in a Session

Scoping to a File and/or a Session

Adding Files to Scoped Patterns

3.3 Context Attributes

3.4 Disposition Attributes

You can provide message pattern information to the ToolTalk service using either dynamic or static methods, or both. The method you choose depends on the type of messages you want to receive.

• If the types of messages you want to receive will vary while your application is running, the dynamic method allows you to add, change, or remove message pattern information after your application has started.

• If you want a message to start your application or to be queued if your application is not running, the static method provides an easy way to specify these instructions. The static method also provides an easy way to specify the message pattern information if you want to receive a defined set of messages. For more information, see Chapter 10, "Static Message Patterns."

3.1 Message Pattern Attributes

Table 3-1 provides a complete list of attributes you can put in your message patterns.

Table 3-1 ToolTalk Message Pattern Attributes

All your message patterns must at least specify:

• Category -- Whether the application wants to perform operations listed in messages or only view messages.
  • Use TT_OBSERVE if you only want to observe messages.
  • Use TT_HANDLE if you want to perform operations requested by the messages.

• Scope -- Whether the application is interested in messages about a particular session or file.
  • Use TT_SESSION to receive messages from other processes in your session.
  • Use TT_FILE to receive messages about the file you have joined.
  • Use TT_FILE_IN_SESSION to receive messages for the file you have joined while in this session.
  • Use TT_BOTH to receive both messages for the file, the session, or the file and the session you have joined.

• The ToolTalk service counts the message attribute as matched if:
  • No pattern attribute is specified.
  • The pattern does not name a context slot.
  • The pattern has an empty context slot.

  The fewer pattern attributes you specify, the more messages you become eligible to receive.

• If there are multiple values specified for a pattern attribute, one of the values must match the message attribute value. If no value matches, the ToolTalk service will not consider your application as a receiver.

• If context slots are contained in the message, the ToolTalk service will not consider your application as a receiver unless:
  • A value specified in a context slot of a pattern matches the value specified in the message context slot.
  • When multiple context slots are specified in a message, each context slot value in the message matches a corresponding context slot value in the pattern.

3.2 Scope Attributes

1. Scope to a session only.

2. Scope to a file only.

3. Scope only to a file in a particular session.

4. Scope to either or both a file and a session.

Scoping to a Session Only

Code Example 3-1 shows a static session-scoped pattern; Code Example 3-2 shows a dynamic session-scoped pattern.

Code Example 3-1 Static Session-Scoped Pattern

Code Example 3-2 Dynamic Session-Scoped Pattern with a File Attribute

Scoping to a File Only

Code Example 3-3 Static File-Scoped Pattern

Code Example 3-4 Dynamic File-Scoped Pattern

Scoping to a File in a Session

Code Example 3-5 Adding a Session to the TT_FILE_IN_SESSION-Scoped Pattern

Code Example 3-6 registers the pattern and then joins a session.

Code Example 3-6 Joining a Session to Set the Session of a TT_FILE_IN_SESSION-Scoped Pattern

Code Example 3-7 sets the scope value for a static pattern.

Code Example 3-7 Setting the Scope Value for a TT_FILE_IN_SESSION Static Pattern

Scoping to a File and/or a Session

Code Example 3-8 A Dynamic Pattern that Uses the TT_BOTH Scope

Code Example 3-9 A Static Pattern that Uses the TT_BOTH Scope

Adding Files to Scoped Patterns

Code Example 3-10 Adding Two File Attributes to a Session-Scoped Pattern

3.3 Context Attributes

You can use contexts to associate arbitrary pairs with ToolTalk messages and patterns, and to restrict the set of possible recipients of a message. One common use of the restricted pattern matching provided by ToolTalk context attributes is to create sub-sessions. For example, two different programs could be debugged simultaneously with tools such as a browser, an editor, a debugger, and a configuration manager active for each program. The message and pattern context slots for each set of tools contain different values; the normal ToolTalk pattern matching of these values keep the two sub-sessions separate.

Another use for the restricted pattern matching provided by ToolTalk context attributes is to provide information in environment variables and command line arguments to tools started by the ToolTalk service.

3.4 Disposition Attributes

The disposition value specified in the static type definition of a pattern is the default disposition; however, if the message deposition specifies the handler ptype the default disposition value is over-ridden. For example, a message disposition specifies a static type definition for the ptype UWriteIt which includes the message signature Display. This message signature does not match any of the static signatures in the pattern. The ToolTalk service will follow the instructions for the disposition set in the message; for example, if the message disposition is TT_START and the UWriteIt ptype specifies a start string, the ToolTalk service will start an instance of the application if one is not running.