- Parts of a Task

A Task is composed of the following building blocks:

A Task name. A Task name can contain up to 32 alphanumeric characters. PROIV assigns "TK_" as a prefix to the task name leaving up to 29 additional characters to use when naming a task. If you exceed the 29-character limit, PROIV deletes the characters from the end of the name.

For example, the task name:

ASAMPLEAPPLICATIONNAMEFORTASKS12

contains 32 characters. PROIV registers that name as:

TK_ASAMPLEAPPLICATIONNAMEFORTASK

In other respects, Task names are just like function names: they can only be distinguished by the location of their definitions in the database, they must be unique, and they must be different from any existing function names.

A list of functions, i.e. a Task List. The Task List can be either an 'inclusive' list or an 'exclusive' list.
An Inclusive List defines those functions that may be executed as part of the Task. If another function is linked-to (that is outside the list), the Task is finished before that function is executed. Called functions are viewed as subroutines of the calling function, and need not be defined in the list. The Function List is unordered; it says nothing about the order in which functions are to be executed. It just defines function membership in the Task. A specific function can belong to more than one Task.
An Exclusive List defines those functions that, if linked to, cause the Task to be finished before executing the specified function. An Exclusive List can be empty, in which case the Task Exit function must be specified. The Task terminates when the Task Exit function is executed.
A mandatory Entry function - when the Task is invoked, this is the first function executed. This normally links to another function.
An optional Exit function - when the Task has ended, the Exit function is executed before returning control to the caller. The Task Exit function must be specified if an empty Exclusive Task List is defined.
An optional Error function - if the application or kernel detects a fatal error, the Task Error function is executed instead of the Task Exit function.
An interface - consisting of an optional Task Parameter List. Task Parameters are made accessible to the functions in a Task through a process called 'mapping'. Each parameter is identified as input (passed to the Task from the Task requester), output (returned to the Task requestor), both input and output, or global (space is allocated and is available to functions but no argument is passed in or out of the Task).

Tasks can also have parameters, which can be used to pass data between the calling application and the Task member functions.

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Topic ID: 540107