Role Forgetting for ALCOQH(O)-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. While 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 in ontologies expressible
in the description logic ALCOQH(O), i.e., the
basic description logic ALC extended with nominals,
qualified number restrictions, role inclusions
and the universal role. Being based on an Ackermann
approach, the method is the only approach so
far for forgetting role symbols in description logics
with qualified 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.