DL-Lite: tractable description logics for ontologies

TLDR

The paper proposes DL‑Lite, a Description Logic designed to capture basic ontology languages while maintaining low reasoning complexity. DL‑Lite achieves efficient reasoning by separating TBox and ABox processing, allowing TBox reasoning to be independent of data and enabling ABox queries to be executed via SQL engines for database optimization. The authors demonstrate that DL‑Lite supports polynomial‑time subsumption, satisfiability, and conjunctive query answering, establishing the first polynomial data‑complexity result for DL knowledge bases.

Abstract

We propose a new Description Logic, called DL-Lite, specifically tailored to capture basic ontology languages, while keeping low complexity of reasoning. Reasoning here means not only computing subsumption between concepts, and checking satisfiability of the whole knowledge base, but also answering complex queries (in particular, conjunctive queries) over the set of instances maintained in secondary storage. We show that in DL-Lite the usual DL reasoning tasks are polynomial in the size of the TBox, and query answering is polynomial in the size of the ABox (i.e., in data complexity). To the best of our knowledge, this is the first result of polynomial data complexity for query answering over DL knowledge bases. A notable feature of our logic is to allow for a separation between TBox and ABox reasoning during query evaluation: the part of the process requiring TBox reasoning is independent of the ABox, and the part of the process requiring access to the ABox can be carried out by an SQL engine, thus taking advantage of the query optimization strategies provided by current DBMSs.