An Efficient Indefiniteness Inference Scheme in Indefinite Deductive Databases

We introduce an inference scheme, based on the compilation approach, that can answer “true,” provable-false,” “indefinite,” or “assumable-false” to a closed query in an indefinite deductive database under the generalized closed world assumption. The inference scheme proposed in this paper consists of a representation scheme and an evaluation process that uses one of two groups of positive indefinite ground clauses (PIGC's) derivable from the database for a given query. These two groups of PIGC's are base-PIGC's and descendants of base-PIGC's. We prove that the set of base-PIGC's derivable from the database is sufficient to infer the indefiniteness of a query. This newly proposed method offers many advantages over the existing compilation method. This new method outperforms the existing one in terms of the cost of compilation, ease in the handling of updates, and efficiency in query evaluation.