We show how to interoperate, semantically and inferentially, between the leading Semantic Web approaches to rules (RuleML Logic Programs) and ontologies (OWL/DAML+OIL Description Logic) via analyzing their expressive intersection. To do so, we define a new intermediate knowledge representation (KR) contained within this intersection: Description Logic Programs (DLP), and the closely related Description Horn Logic (DHL) which is an expressive fragment of first-order logic (FOL). DLP provides a significant degree of expressiveness, substantially greater than the RDFSchema fragment of Description Logic.We show how to perform DLP-fusion: the bidirectional translation of premises and inferences (including typical kinds of queries) from the DLP fragment of DL to LP, and vice versa from the DLP fragment of LP to DL. In particular, this translation enables one to "build rules on top of ontologies": it enables the rule KR to have access to DL ontological definitions for vocabulary primitives (e.g., predicates and individual constants) used by the rules. Conversely, the DLP-fusion technique likewise enables one to "build ontologies on top of rules": it enables ontological definitions to be supplemented by rules, or imported into DL from rules. It also enables available efficient LP inferencing algorithms/implementations to be exploited for reasoning over large-scale DL ontologies.

Abstract. Ontologies as means for conceptualizing and structuring domain knowledge within a community of interest are seen as a key to realize the Semantic Web vision. However, the decentralized nature of the Web makes achieving this consensus across communities difficult, thus, hampering efficient knowledge sharing between them. In order to balance the autonomy of each community with the need for interoperability, mapping mechanisms between distributed ontologies in the Semantic Web are required. In this paper we present MAFRA, an interactive, incremental and dynamic framework for mapping distributed ontologies in the Semantic Web.

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Abstract. This paper discusses issues that surround the provision of application support using OWL ontologies. It presents the OWL API, a high-level programmatic interface for accessing and manipulating OWL ontologies. We discuss the underlying design issues and illustrate possible solutions to technical issues occurring in systems that intend to support the OWL standard. Although the context of our solutions is that of a particular implementation, the issues discussed are largely independent of this and should be of interest to a wider community.

Abstract. This paper introduces a visual, UML-based notation for OWL ontologies. We provide a standard MOF2 compliant metamodel which captures the language primitives offered by OWL DL. Similarly, we invent a UML profile, which allows to visually model OWL ontologies in a notation that is close to the UML notation. This allows to develop ontologies using UML tools. Throughout the paper, the significant differences to some earlier proposals for a visual, UML-based notation for ontologies are discussed.

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