APRIL: a flexible production rule interpreter

A general purpose Production System interpreter, APRIL, has been developed to model aspects of students problem solving in a CAI environment. APRIL incorporates most of the facilities common to earlier interpreters and also includes several additional features. One new feature allows "high-level" routines, such as those used by the interpreter itself in the matching and cycling phases, to be actions in production rules: hence it is possible for the user to "create" an interpreter which is suitable for his particular domain. However, the most important features of APRIL are that: 1) memory is handled uniformly (Production Rules and data both being stored as states) and 2) APRIL allows Production Rules to retrieve and modify any state. Together these latter features allow adaptive systems to be implemented.