The value of the variable *inferencing-state* is known as the current inferencing state. Its value can be changed before calling KnowledgeWorks functions, but should not be changed within the body of a rule.
Some operations, such as object creation, slot modification, reset and infer only affect the current inferencing state. Backward chaining operations that match the object base only find objects from the current inferencing state.
Operations that change rules or contexts, such as defrule and clear-all, affect all inferencing states.
KnowledgeWorks and Prolog User Guide (Unix version) - 6 Dec 2011