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The recently introduced series of description logics under the common moniker 'DL-Lite' has attracted attention of the description logic and semantic web communities due to the low computational complexity of inference, on the one hand, and the ability to represent conceptual modeling formalisms, on the other. The main aim of this article is to carry out a(More)
It is known that for temporal languages, such as first-order LT L, reasoning about constant (time-independent) relations is almost always undecidable. This applies to temporal description logics as well: constant binary relations together with general concept subsumptions in combinations of LT L and the basic description logic ALC cause undecidability. In(More)
We develop a formal framework for comparing different versions of ontologies, and apply it to ontologies formulated in terms of DL-Lite, a family of 'lightweight' description logics designed for data-intensive applications. The main feature of our approach is that we take into account the vocabulary (= signature) with respect to which one wants to compare(More)
The use of ontologies for accessing data is one of the most exciting new applications of description logics in databases and other information systems. A realistic way of realising sufficiently scalable on-tology-based data access in practice is by reduction to querying relational databases. In this paper, we describe the combined approach, which(More)
We investigate the computational complexity of reasoning over various fragments of the Extended Entity-Relationship (EER) language, which includes a number of constructs: ISA between entities and relationships, disjointness and covering of entities and relationships, cardinality constraints for entities in relationships and their refinements as well as(More)
We present the architecture and technologies underpinning the OBDA system Ontop and taking full advantage of storing data in relational databases. We discuss the theoretical foundations of Ontop: the tree-witness query rewriting, T-mappings and optimisations based on database integrity constraints and SQL features. We analyse the performance of Ontop in a(More)
We present a formal framework for (minimal) module extraction based on an abstract notion of in-separability w.r.t. a signature between ontologies. Two instances of this framework are discussed in detail for DL-Lite ontologies: concept inseparabil-ity, when ontologies imply the same complex concept inclusions over the signature, and query in-separability,(More)
Our aim is to investigate ontology-based data access over temporal data with validity time and ontologies capable of temporal conceptual modelling. To this end, we design a temporal description logic, TQL, that extends the standard ontol-ogy language OWL 2 QL, provides basic means for temporal conceptual modelling and ensures first-order rewritability of(More)
We design temporal description logics (TDLs) suitable for reasoning about temporal conceptual data models and investigate their computational complexity. Our formalisms are based on <i>DL-Lite</i> logics with three types of concept inclusions (ranging from atomic concept inclusions and disjointness to the full Booleans), as well as cardinality constraints(More)