Ontologies provide a conceptualization of a domain of interest. Nowadays, they are typically represented in terms of Description Logics, and are seen as the key technology used to describe the semantics of information at various sites. The idea of using ontologies as a conceptual view over data repositories is becoming more and more popular. In order for this idea to become widespread in standard applications, it is fundamental that the conceptual layer through which the underlying data layer is accessed does not introduce a significant overhead in dealing with the data. Based on these observations, in recent years techniques to access data sources through a conceptual layer built on top of them have been developed, and the computational complexity of answering queries over ontologies, measured in the size of the underlying data, has been studied.
The talk is divided in two parts. The first part will present the general ideas underlying ontology mediated data management, and will discuss the tradeoff between expressive power of the ontology language, and efficiency in query processing. We will specifically address the possibility of delegating query processing over ontologies to database engines of increasing power (from relational, to linear recursion, to arbitrary recursion, to disjunctive Datalog). In the second part, we will provide a concrete example of a system for ontology mediated data management on top of a relational engine. The system is implemented in the prototype tool QuOnto.
The talk will be jointly given by Diego Calvanese and Giuseppe De Giacomo.