Alexandra Poulovassilis

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From: Data & Knowledge Engineering Volume 28, Pages 47--71, Elsevier, 1998 Several methodologies for integrating database schemas have been proposed in the literature, using various common data models (CDMs). As part of these methodologies transformations have been defined that map between schemas which are in some sense equivalent. This paper describes a(More)
XML repositories are now a widespread means for storing and exchanging information on the Web. As these repositories become increasingly used in dynamic applications such as e-commerce, there is a rapidly growing need for a mechanism to incorporate reactive functionality in an XML setting. Event-condition-action (ECA) rules are a technology from active(More)
The Semantic Web is based on XML and RDF as standards for exchanging and storing information on the World Wide Web. Event-Condition-Action rules are a possible candidate technology for distributed web-based applications that require timely notification and propagation of events and information between different sites. This paper discusses the provision of(More)
RDF is becoming a core technology in the Semantic Web. Providing the ability to describe metadata information that can be easily navigated, and the ease of storing it in existing relational database systems, have made RDF a very popular way of expressing and exchanging metadata information. However, the use of RDF in dynamic applications over distributed(More)
Three recent trends in database research are object-oriented and deductive databases and graph-based user interfaces. We draw these trends together in a data model we call the Hypernode Model. The single data structure of this model is the <italic>hypernode</italic>, a graph whose nodes can themselves be graphs. Hypernodes are typed, and types, too, are(More)
We explore flexible querying of RDF data, with the aim of making it possible to return data satisfying query conditions with varying degrees of exactness, and also to rank the results of a query depending on how “closely” they satisfy the query conditions. We make queries more flexible by logical relaxation of their conditions based on RDFS entailment and(More)