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
r. Kurt Bollacker is a computer scientist with a research background in the areas of machine learning, digital libraries, semantic networks, and electro-cardiographic modeling. He received a Ph.D. in Computer Engineering from The University Of Texas At Austin, was co-creator of the Citeseer research tool as a visiting researcher at the NEC Research Institute, was the technical director of the Internet Archive, and a biomedical research engineer at the Duke University Medical Center. He is currently pursuing research into long term digital archiving as the Digital Research Director at the Long Now Foundation, and is a scientist at Metaweb Technologies.
M. Huchard, A. Napoli, M. Hacene, и P. Valtchev. Selected Contributions in Data Analysis and Classification, Studies in Classification, Data Analysis, and Knowledge Organization, (октября 2007)