Vladislav Ryzhikov

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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 extend the DL-Lite languages by means of attributes and datatypes. Attributes—a notion borrowed from data models— associate concrete values from datatypes to abstract objects and in this way complement roles, which describe relationships between abstract objects. The extended languages remain tractable (with a notable exception) even though they contain(More)
We investigate conjunctive query inseparability of description logic (DL) knowledge bases (KBs) with respect to a given signature, a fundamental problem for KB versioning, module extraction, forgetting and knowledge exchange. We study the data and combined complexity of deciding KB query inseparability for fragments of Horn-ALCHI, including the DLs(More)
We introduce and investigate a number of fragments of propositional temporal logic LTL over the flow of time (Z, <). The fragments are defined in terms of the available temporal operators and the structure of the clausal normal form of the temporal formulas. We determine the computational complexity of the satisfiability problem for each of the fragments,(More)
In this paper, we study the problem of exchanging knowledge between a source and a target knowledge base (KB), connected through mappings. Differently from the traditional database exchange setting, which considers only the exchange of data, we are interested in exchanging implicit knowledge. As representation formalism we use Description Logics (DLs), thus(More)
The DL-Lite family of description logics has recently been proposed and investigated in [5–7] and later extended in [1, 8, 3]. The relevance of the DL-Lite family is witnessed by the fact that it forms the basis of OWL 2 QL, one of the three profiles of OWL 2 (http://www.w3.org/TR/owl2-profiles/). According to the official W3C profiles document, the purpose(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)
We investigate the temporal extension of the description logic DL-Lite bool with the until operator on concepts, rigid (time-independent) and local (time-dependent) roles, and rigid TBox axioms. Using an embedding into the one-variable fragment of first-order temporal logic and the quasimodel technique, we prove that (i) the satisfiability problem for the(More)