Michael Wessel

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We summarize the results we obtained on the extensions of ALC with composition-based role inclusion axioms of the form ST v R 1 t tR n. A set of these role axioms is called a role box. The original motivation for this work was to develop a description logic suitable for qualitative spatial reasoning problems. We quickly deene and discuss the DLs ALC RA ,(More)
Practical description logic systems play an ever-growing role for knowledge representation and reasoning research even in distributed environments. In particular, the ontology layer of the often-discussed semantic web is based on description logics (DLs) and defines important challenges for current system implementations. The article introduces and(More)
In this paper the description logic ALCNHR+(D) is introduced. Prominent language features beyond conjunction, full negation, and quantifiers are number restrictions, role hierarchies, transitively closed roles, generalized concept inclusions, and concrete domains. As in other languages based on concrete domains (e.g. ALC(D)) a so-called existential(More)
This paper reports on a pragmatic query language for Racer. The abstract syntax and semantics of this query language is defined. Next, the practical relevance of this query language is shown, applying the query answering algorithms to the problem of consistency maintenance between object-oriented design models.
In this paper, we consider the problem of query answering over large multimedia ontologies. Traditional reasoning systems may have problems to deal with large amounts of expressive ontological data (terminological as well as assertional data) that usually must be kept in main memory. We propose to overcome this problem with a new so-called filter and refine(More)
The recent success of distributed and dynamic infrastructures for knowledge sharing has raised the need for semiautomatic/automatic ontology evolution strategies. Ontology evolution is generally defined as the timely adaptation of an ontology to changing requirements and the consistent propagation of changes to dependent artifacts. In this article, we(More)