Rewriting Conjunctive Queries under Description Logic Constraints

Rewriting Conjunctive Queries under Description Logic Constraints ( Technical Report )

We consider the problems of conjunctive query answering and rewriting under Description Logic constraints. We present a query rewriting algorithm for ELHI knowledge bases, and use it to show that query answering in this setting is PTime-complete w.r.t. data complexity. We show that our algorithm is worst-case optimal for languages with data complexity of query answering ranging from LogSpace to...

Tractable query answering and rewriting under description logic constraints

Answering queries over an incomplete database w.r.t. a set of constraints is an important computational task with applications in fields as diverse as information integration and metadata management in the semantic Web. Description Logics (DLs) are constraint languages that have been extensively studied with the goal of providing useful modeling constructs while keeping the query answering prob...

First Order-Rewritability and Containment of Conjunctive Queries in Horn Description Logics

We study FO-rewritability of conjunctive queries in the presence of ontologies formulated in a description logic between EL and Horn-SHIF , along with related query containment problems. Apart from providing characterizations, we establish complexity results ranging from EXPTIME via NEXPTIME to 2EXPTIME, pointing out several interesting effects. In particular, FO-rewriting is more complex for c...

Rewriting Conjunctive Queries using Views in Description Logics with Existential Restrictions

Query Rewriting under Linear EL Knowledge Bases

With the adoption of the recent SPARQL 1.1 standard, RDF databases are capable of directly answering more expressive queries than simple conjunctive queries. We exploit such capabilities to answer conjunctive queries (CQs) under ontologies expressed in the description logic called linear EL , a restricted form of EL. In particular, we show a query answering algorithm that rewrites a given CQ in...