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In many data-centric applications, it is desirable to use OWL as an expressive schema language with which one expresses constraints that must be satisfied by instance data. However, specific aspects of OWL's standard semantics—i.e., the Open World Assumption (OWA) and the absence of Unique Name Assumption (UNA)—make it difficult to use OWL in this way. What(More)
Context modeling is critical for the unambiguous and effective delivery of data and knowledge on the Web, and in particular, the Semantic Web. However, Contexts are often embedded in the application programs or are implied by the application-or community-specific agreements. In this paper, we propose a framework for contexts modeling that can provide formal(More)
As semantic web technologies are increasingly used to empower knowledge management systems (KMSs), there is a growing need for mechanisms and automated tools for checking content generated by semantic-web tools. The content in a KMS includes both the knowledge management (KM) schema and the data contained within. KM schemas can be viewed as ontologies and(More)
OWL instance data evaluation, identified by our previous work, is to check whether the instance data conforms to the semantic expectation of its targeting applications. We have identified some integrity issues raised by applications demanding closed world reasoning. In this paper, we present a formal characterization of those integrity issues using(More)
Many emerging semantic web applications include ontologies from one set of authors and instance data from another (often much larger) set of authors. Often ontologies are reused and instance data is integrated in manners unanticipated by their authors. Not surprisingly, many instance data rich applications encounter instance data that is not compatible with(More)
This paper presents our work on supporting evaluation of integrity constraint issues in semantic web instance data. We propose an alternative semantics for the ontology language, i.e., OWL, a decision procedure for constraint evaluation by query answering, and an approach of explaining and repairing integrity constraint violations by utilizing the(More)
Grid has emerged as a new paradigm for integration within dynamic virtual enterprises. Given a service-oriented Grid environment, more complex, value-added sophisticated services and applications can be built via service composition. In this paper, we discuss Grid services composition by leveraging Semantic Web services standards and technology , especially(More)