01631nas a2200181   4500008004100000245004400041210004400085300000600129490000700135520112800142653002901270653002301299653001501322100002201337700002301359700002001382856004701402       2013                        eng d00aComplexities of Horn Description Logics0 aComplexities of Horn Description Logics  a20 v143 aDescription Logics (DLs) have become a prominent paradigm for representing knowledge bases in a variety of application areas. Central to leveraging them for corresponding systems is the provision of a favourable balance between expressivity of the knowledge representation formalism on the one hand, and runtime performance of reasoning algorithms on the other. Due to this, Horn description logics (Horn DLs) have attracted attention since their (worst-case) data complexities are in general lower than their overall (i.e. combined) complexities, which makes them attractive for reasoning with large sets of instance data (ABoxes). However, the natural question whether Horn DLs also provide advantages for schema (TBox) reasoning has hardly been addressed so far. In this paper, we therefore provide a thorough and comprehensive analysis of the combined complexities of Horn DLs. While the combined complexity for many Horn DLs studied herein turns out to be the same as for their non-Horn counterparts, we identify subboolean DLs where Hornness simplifies reasoning. We also provide convenient normal forms for Horn DLs.10acomputational complexity10adescription logics10aHorn logic1 aKrötzsch, Markus1 aRudolph, Sebastian1 aHitzler, Pascal  uhttp://doi.acm.org/10.1145/2422085.242208701673nas a2200229   4500008004100000245005800041210005500099260002500154490000800179520100400187653002001191653001701211653001701228653002201245100002101267700002001288700002001308700002101328700002301349700002701372856004401399       2011                        eng d00aLocal Closed World Semantics: Keep it simple, stupid!0 aLocal Closed World Semantics Keep it simple stupid  bCEUR-WS.orgc07/20110 v7453 aA combination of open and closed-world reasoning (usually called local closed world reasoning) is a desirable capability of knowledge representation formalisms for Semantic Web applications. However, none of the proposals made to date for extending description logics with local closed world capabilities has had any significant impact on applications. We believe that one of the key reasons for this is that current proposals fail to provide approaches which are intuitively accessible for application developers and at the same time are applicable, as extensions, to expressive description logics such as SROIQ, which underlies the Web Ontology Language OWL. In this paper we propose a new approach which overcomes key limitations of other major proposals made to date. It is based on an adaptation of circumscriptive description logics which, in contrast to previously reported circumscription proposals, is applicable to SROIQ without rendering reasoning over the resulting language undecidable.10acircumscription10aclosed world10adecidability10aDescription Logic1 aKrisnadhi, Adila1 aSengupta, Kunal1 aHitzler, Pascal1 aRosati, Riccardo1 aRudolph, Sebastian1 aZakharyaschev, Michael  uhttp://ceur-ws.org/Vol-745/paper_12.pdf