We extend the description logic EL++ with reflexive roles
and range restrictions, and show that subsumption remains tractable if
a certain syntactic restriction is adopted. We also show that subsumption
becomes PSpace-hard (resp. undecidable) if this restriction is weakened
(resp. dropped). Additionally, we prove that tractability is lost when
symmetric roles are added: in this case, subsumption becomes ExpTime-
hard
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G. Hillairet, F. Bertrand, J. Lafaye, и others. Proceedings of the 4th International Workshop on Semantic Web Enabled Software Engineering, SWESE, (2008)
A. Hildisch, J. Steurer, и R. Stolle. Proceedings of the 4th International Workshop on Software Engineering for Automotive Systems, стр. 4--. Washington, DC, USA, IEEE Computer Society, (2007)