4.3 Task descriptions

Task descriptions are a powerful way of tersely describing the sources and targets of coNCePTuaL operations. Task IDs range from 0 to ‘num_tasks-1’ (see Predeclared variables). Operations involving out-of-bound task IDs are silently ignored.

As a side effect, a task description can declare a variable that can be used in subsequent expressions. (See Expressions.) There are two types of task descriptions: one for “source” tasks and one for “target” tasks. The two are syntactically similar but semantically different. Specifically, the scope of a variable declared in a <target_tasks> specification is more limited than one declared in a <source_task> specification.

Before introducing <source_task> and <target_tasks> specifications we first introduce the notion of a <restricted_ident>, which is a variable declaration that can be used to define a set of tasks. We then present coNCePTuaL’s complete set of mechanisms for describing sets of source and target tasks.