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2.2 The user interface and the GWAM

The user interface has four promptsgif: ``rfi-p;SPMgt; '' or ``rfi-l;SPMgt; '' is displayed when the queries are sent to the interpreter and its database, while ``rfe-p> '' and ``rfe-l> '' show that the query, which is a valued conjunction of math506 literals, will be emulated after compilation. The suffix of the prompt is ``-p;SPMgt; '' or ``-l;SPMgt; '', respectively, when the system is running in PROLOG or LISP style (see [Her92]). The code obtained is stored under the name main, the data structures for the variables in the query are created and their names and locations are memorized to get the variable names when the goal succeeds. Finally the emulator is called, producing failures or returned values with possible variable bindings. When a goal succeeds, the results are printed; backtracking is invoked if the user's next input is more so that the next solution may be computed. When spy is enabled, the query's compilation is shown and the GWAM is set into debugging (interactive or non-interactive single-step) mode. With nospy this feature is turned off.

Harold Boley (