Consequence Finding in Default Theories

Abstract

Abstract. Consequence finding has been recognized as an important technique in many intelligent systems involving inference. In previous work, propositional or first-order clausal theories have been considered for consequence finding. In this paper, we consider consequence finding within a default theory, which consists of a first-order clausal theory and a set of normal defaults. In each extension of a default theory, consequence finding can be performed with the "generating defaults" for the extension. Alternatively, we consider all extensions in one theory with the "conditional consequence" format, which explicitly represents how a conclusion depends on which defaults. We also propose a procedure to compute consequences from a default theory based on a first-order consequence-finding procedure SOL. The SOL calculus is then further refined using skip-preference and complement checking, which have a great ability of preventing irrational derivations. The proposed system can be well applied to a multi-agent system with speculative computation in an incomplete communication environment.