Evaluation-Based Reasoning with Disjunctive Information in First-Order Knowledge Bases

Abstract In previous work, Levesque proposed anevaluation-based reasoning procedure for so-called proper KBs, equivalent to a possibly in-complete possibly infinite set of function-freeground literals. The procedure, called V ; pre-served the efficiency and logical soundness ofdatabase query evaluation. Moreover, if thequery was constrained to be in a special normalform, V was also logically complete. In this pa-per, we propose an extension to this work to han-dle disjunctive information in a KB. We definea query evaluation procedure X that generalizes V to deal with KBs that are equivalent to a pos-sibly infinite set of function-free ground clauses.Deductive reasoning that is logically sound andcomplete in this case is undecidable in general,and so, we describe what we are willing to giveup in X to preserve tractability. 1 Introduction It was argued in [8] that the only procedure yet proposedto perform deductive reasoning effectively over extremelylarge first-order knowledge bases (KBs) (involving say