Efficient Approximation in DL-Lite of OWL 2 Ontologies

Ontologies, as a conceptualization of a domain of interest, can be used
for different objectives, such as for providing a formal description of the domain
of interest for documentation purposes, or for providing a mechanism for reasoning upon the domain. For instance, they are the core element of the Ontology Based Data Access paradigm, in which the ontology is utilized as a conceptualview, allowing user access to the underlying data sources. With the aim to use an ontology as a formal description of the domain of interest, the use of expressive languages proves to be useful. If instead the goal is to use the ontology for reasoning tasks which require low computational complexity, the high expressivity of the language used to model the ontology may be of hindrance. In this scenario, the approximation of ontologies expressed in very expressive languages through ontologies expressed in languages which keep the computational complexity of the reasoning tasks low is pivotal. In this work we present our notion of ontology approximation and present an algorithm for computing the approximation of OWL 2 ontologies by means of DL-Lite TBoxes. Moreover, we provide optimization techniques for this computation, and discuss the results of the implementation of these techniques.