Role Forgetting for ALCOQH(universal role)-Ontologies Using an Ackermann-Based Approach

Forgetting refers to a non-standard reasoning problem concerned with eliminating concept and role symbols from description logic-based ontologies while preserving all logical consequences up to the remaining symbols. Whereas previous research has primarily focused on forgetting concept symbols, in this paper, we turn our attention to role symbol forgetting. In particular, we present a practical method for semantic role forgetting for ontologies expressible in the description logic ALCOQH(O), i.e., the basic description logic ALC extended with nominals, number restrictions, role inclusions and the universal role. Being based on an Ackermann approach, the method is so far the only approach for forgetting role symbols in description logics with number restrictions. The method is goal-oriented and incremental. It always terminates and is sound in the sense that the forgetting solution is equivalent to the original ontology up to the forgotten symbols, possibly with new concept definer symbols. Despite our method not being complete, performance results of an evaluation with a prototypical implementation have shown very good success rates on real-world ontologies.