----------------------------------------------------------------------------- Functional Constraints in Ontology Reasoning ----------------------------------------------------------------------------- Andrea Cali' University of London & Oxford University ----------------------------------------------------------------------------- Mercoledi' 5 Dicembre 2012 - Ore 11:30 Sala Riunioni Dip. di Informatica e Automazione - Universita' Roma Tre Via Vasca Navale, 79 00146 Roma ----------------------------------------------------------------------------- Sommario When data schemata are enriched with expressive constraints that aim at representing the domain of interest, in order to answer queries one needs to consider the logical theory consisting of both the data and the constraints. Query answering in the presence of constraints that allow for the inference of new information is usually called ontological query answering. Commonly adopted database constraints in this field are tuple-generating dependencies (TGDs) and equality-generating dependencies (EGDs), the latter being in fact functional constraints. It is well known that the interaction of TGDs and EGDs leads to intractability or undecidability of query answering even in the case of simple subclasses. The main (semantic) condition that guarantees a loose interaction between these two types of constraints is called separability. Separability often guarantees tractability, as long as the theory is satisfiable. In this talk we review the main notions of separability found in the literature, as well as several syntactic conditions that are sufficient to prove them. We then shed light on the issue of satisfiability checking, showing that under a sufficient condition called deep separability it can be done by considering the TGDs only. We show that, fortunately, in the case of TGDs and EGDs, separability implies deep separability. This result generalizes several analogous ones, proved ad hoc for particular classes of constraints. We show the results of some preliminary experiments on a prototype system. -----------------------------------------------------------------------------