CK-LOG, A Calculus for Knowledge Processing in Logic.

摘要

This paper introduces the principal concepts in the organization and operation of the logic based knowledge processing system called CK-LOG (A Calculus for Knowledge in LOGic) CK-LOG uses the frame based system MDS (the Meta Description System) for knowledge representation and for modelling world states. It uses an inference engine based on Natural Deduction for stating and solving problems. As a knowledge processing system CK-LOG has several capabilities which are new to the technology of knowledge representation systems. CK-LOG has special facilities to represent and reason about actions and their time dependencies. Actions that occur in a world state may create or destroy objects in the world or modify their properties or prevent or support other actions. The effects of actions are described in CK-LOG using modal operators like CREATE, DESTROY, PREVENT, SUPPORT, KEEP, etc. These operator expressions are also used to represent and reason about possible worlds that the actions might lead to. Most significantly, CK-LOG is a logic based knowledge processing system, just as PROLOG is a logic based programming system. CK-LOG uses a three valued logical system with truth values T (true), (unknown) and F (false) to build partial models of world states, and the two valued logical system of T and F in its theorem proving system. The use of the three valued logical system in its models of world states enables CK-LOG to do problem solving in the context of incomplete information about world states.