Node:Query Classes, Next:, Up:Query Processing

Query Classes

Queries posed by the system can be classified according to the kind of input they expect, the way the input is processed, etc. Queries of the same kind form a query class.

For example, queries requiring a yes/no answer form a query class with the following characteristics:

There are built-in query classes for reading in yes/no answers, toplevel queries, debugger commands, etc.

A query class is characterized by a ground Prolog term, which is supplied as the first argument to the query processing predicate ask_query/4. The characteristics of a query class are normally described by the extendible predicate

'SU_messages':query_class(+QueryClass, -Prompt, -InputMethod,
                          -MapMethod, -FailureMode).

The arguments of the query_class predicate have the following meaning: