Decidability of SHIQ with Complex Role Inclusion Axioms

Motivated by medical terminology applications, we investigate the decidability of the well known expressive DL, SHIQ, extended with role inclusion axioms (RIAs) of the form R ◦ S v P . We show that this extension is undecidable even when RIAs are restricted to the forms R◦S v R or S ◦R v R, but that decidability can be regained by further restricting RIAs to be acyclic. We present a tableau algorithm for this DL and report on its implementation, which behaves well in practise and provides important additional functionality in a medical terminology application.