Maurizio Lenzerini

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We propose a new family of description logics (DLs), called DL-Lite, specifically tailored to capture basic ontology languages, while keeping low complexity of reasoning. Reasoning here means not only computing subsumption between concepts and checking satisfiability of the whole knowledge base, but also answering complex queries (in particular, unions of(More)
Data integration is the problem of combining data residing at different sources, and providing the user with a unified view of these data. The problem of designing data integration systems is important in current real world applications, and is characterized by a number of issues that are interesting from a theoretical point of view. This document presents(More)
One of the fundamental principles of the database approach is that a database allows a nonredundant, unified representation of all data managed in an organization. This is achieved only when methodologies are available to support integration across organizational and application boundaries. Methodologies for database design usually perform the design(More)
Many organizations nowadays face the problem of accessing existing data sources by means of flexible mechanisms that are both powerful and efficient. Ontologies are widely considered as a suitable formal tool for sophisticated data access. The ontology expresses the domain of interest of the information system at a high level of abstraction, and the(More)
We propose a new Description Logic, called DL-Lite, specifically tailored to capture basic ontology languages, while keeping low complexity of reasoning. Reasoning here means not only computing subsumption between concepts, and checking satisfiability of the whole knowledge base, but also answering complex queries (in particular, conjunctive queries) over(More)
In this paper we study data complexity of answering conjunctive queries over DL knowledge bases constituted by an ABox and a TBox. In particular, we characterize the LogSpace boundary (over the data) of the problem. This boundary is particularly meaningful because, when we go above it, query answering is not expressible as a first-order logic formula (and(More)
We present an integrated system for knowledge representation, calledAL -log, based on description logics and the deductive database language Datalog. AL-log embodies two subsystems, called structural and relational. The former allows for the definition of structural knowledge about classes of interest (concepts) and membership relation between objects and(More)
Query containment under constraints is the problem of checking whether for every database satisfying a given set of constraints, the result of one query is a subset of the result of another query, Recent research points out that this is a central problem in severa database applications, and we address it within A setting where constraints are specified in(More)
tively used in the construction of knowledge-based applications in several domains (see for example Wright et al. 1993), like connguration and software engineering. Recently we have seen attempts to use them in the elds of machine learning (see for example Cohen and Hirsh 1994) and planning (see for example Devambu and Litman 1991, Weida and Litman 1992,(More)
ur K ¨ unstliche In-telligenz, DFKI) with sites in Kaiserslautern and Saarbrücken is a non-profit organization which was founded in 1988. The DFKI conducts application-oriented basic research in the field of artificial intelligence and other related subfields of computer science. The overall goal is to construct systems with technical knowledge and common(More)