Computing Minimal Projection Modules for Conjunctive Queries

We consider the problem of extracting modules of an ontology that contains the knowledge as represented by a second ontology. The knowledge to be preserved is specified using entailment of conjunctive queries over a given vocabulary. We propose a novel module notion called projection module that preserves the answers to conjunctive queries as they follow from a reference ontology. We present an algorithm for computing minimal projection modules for conjunctive queries. As target and reference ontology we take ELHr-terminologies. The algorithm is based on simulation notions developed for detecting logical differences between ELHr-terminologies.