We will concentrate on presenting background that is directly relevant to the work presented here. This means that the system can access and reason about the representations of factual and problem-solving knowledge and about their interactions. Every concept or class can have a definition that intensionally describes the set of objects that belong to that class. Concept descriptions can include type and number restrictions of the fillers for relations to other concepts.
Relations can also have definitions.
Factual knowledge includes the concept base, the instance base, and the relations among them. Subgoals that arise during problem solving are solved by methods. Some method bodies are calls to Lisp functions that are executed without further subgoaling. The upper part of the picture shows factual knowledge that is domain independent and can be reused for any domain. The state is described with a set of variables.