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It is well-known that inconsistency causes severe problems in classical logic. In particular, since an inconsistent logical theory has no model, it logically implies every formula, and, therefore, query answering on an inconsistent knowledge base becomes meaningless. In this paper, we address the problem of dealing with inconsistencies in Description Logic(More)
In this paper we present Mastro, a Java tool for ontology-based data access (OBDA) developed at the Sapienza Università di Roma and at the Free University of Bozen-Bolzano. Mastro manages OBDA systems in which the ontology is specified in DL-LiteA,id , a logic of the DL-Lite family of tractable Description Logics specifically tailored to ontology-based data(More)
Ontology-based data access (OBDA) is receiving great attention as a new paradigm for managing information systems through semantic technologies. According to this paradigm, a Description Logic ontology provides an abstract and formal representation of the domain of interest to the information system, and is used as a sophisticated schema for accessing the(More)
The task of an <i>information integration system</i> is to combine data residing at different sources, providing the user with a unified view of them, called <i>global schema.</i> Users formulate queries over the global schema, and the system suitably queries the sources, providing an answer to the user, who is not obliged to have any information about the(More)
In this paper we study the problem of obtaining meaningful answers to queries posed over inconsistent DL-Lite ontologies. We consider different variants of inconsistency-tolerant semantics and show that for some of such variants answering unions of conjunctive queries (UCQs) is first-order (FOL) rewritable, i.e., it can be reduced to standard evaluation of(More)
The goal of data integration is to provide a uniform access to a set of heterogeneous data sources, freeing the user from the knowledge about where the data are, how they are stored, and how they can be accessed. One of the outcomes of the research work carried out on data integration in the last years is a clear conceptual architecture, comprising a global(More)
In Ontology Based Data Access (OBDA), the aim is to use an ontology to mediate access to data. The main contribution of this work is to demonstrate two key components of an OBDA system, whose combination allows ontology practitioners to finally realize end-to-end OBDA systems. The first component is an OBDA-enabled reasoner, named DIG-MASTRO. The second(More)
In this paper we present the Quonto Inconsistent Data handler (QuID). QuID is a reasoner for OWL 2 QL that is based on the system Quonto and is able to deal with inconsistent ontologies. The central aspect of QuID is that it implements two different, orthogonal strategies for dealing with inconsistency: ABox repairing techniques, based on data manipulation,(More)
In this paper we present Mastro, a Java tool for ontologybased data access (OBDA) developed at Sapienza Università di Roma. Mastro manages OBDA systems in which the ontology is specified in a logic of the DL-Lite family of Description Logics specifically tailored to ontology-based data access, and is connected to external data management systems through(More)
In ontology-based data access (OBDA), an ontology is connected to autonomous, and generally pre-existing, data repositories through mappings, so as to provide a high-level, conceptual view over such data. User queries are posed over the ontology, and answers are computed by reasoning both on the ontology and the mappings. Query answering in OBDA systems is(More)