Ontology schema for an agent belief store

Keith L. Clark and Frank G. McCabe

Abstract

In this paper we explore the use of a formal Owl ontology as a constraining framework for the belief store of a rational agent. The static beliefs of the agent are the axioms of the ontology. The dynamic beliefs are the descriptions of the individuals that are instances of the ontology classes. The individuals all have a unique identifier, an associated set of named classes to which they are believed to belong, and a set of property values. The ontology axioms act as a schema for the dynamic beliefs. Belief updates not conforming to the axioms lead to either rejection of the update or some other revision of the dynamic belief store to maintain consistency. Partial descriptions are augmented by inferences of property values and class memberships licensed by the axioms.

For concreteness we sketch how such an ontology based agent belief store could be implemented in a multi-threaded logic programming language with imperative and object oriented programming features called Go!. This language was specifically designed for implementing communicating rational agent applications. We shall see that its Prolog style rules allow us to considerable enrich the ontology with rule defined n-ary relations and functions.

For inferences licensed by the ontology we shall use a combination of forward and backward chaining deduction, with justifications associated with each dynamically asserted fact. The justifications are used in the pragmatics of consistency maintenance, an issue not normally considered by the ontology community, and to allow any inferred asserted facts to be automatically removed when one of the facts from which they were derived is removed.

The paper assumes some familiarity with ontology specification using languages such as Owl and with logic programming.

KEYWORDS: Labeled theories, object-oriented logic programming, ontology repesentation

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