Worst-case Optimal Conjunctive Query Answering for an Expressive Description Logic without Inverses

Answering conjunctive queries (CQs) has been recognized as a key task for the usage of Description Logics (DLs) in a number of applications, and has thus been studied by many authors. In this paper, we present an algorithm for this problem in the DL ALCH which works in exponential time. It improves over previous algorithms which require double exponential time and is worst-case optimal, as already satisfiability testing in ALC is EXPTIME-complete. Furthermore, it shows that inverse roles cause an exponential jump in complexity; as recently shown, the problem is 2EXPTIMEcomplete for ALCI. The algorithm is based on a technique

• Type: Conference
• Year: 2008
• Where: AAAI
• Authors: Magdalena Ortiz, Mantas Simkus, Thomas Eiter
• Keywords: AAAI 2008, Conjunctive Queries, Double Exponential Time, Exponential Time, Intelligent Agents