Ontology Based Query Answering: The Story So Far.
Magdalena Ortiz · 2013
Abstract. Databases where relations have arity at most two, often called graph databases, play a prominent role in many fields. Ontology languages based on Description Logics (DLs) have been advocated to enrich such repositories (known as ABoxes in DL jargon) with ontological information. Then, in Ontology Based Query Answering (OBQA), one is interested in answering user queries over the data while taking into account the ontology. However, the ontological layer has a significant effect on the query answering problem, and OBQA algorithms are usually more involved than their counterparts in plain (graph) databases. The development of OBQA algorithms and their implementation has been the goal of significant research efforts in the DL community in the last decade. Here we review some of the achieved results. We discuss the main challenges to be overcome when the ontological knowledge is expressed in different DLs, and when different query languages are considered. We give an overview of some of the algorithms developed so far, and the computational complexity of the problem for the different combinations of DLs and query languages. 1