Manolis Gergatsoulis

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An unfold/fold program transformation system which extends the unfold/fold transformations of H. Tamaki and T. Sato is presented in this paper. The system consists of unfolding, simultaneous folding , and generalization + equality introduction rules. The simultaneous folding rule permits the folding of a set of folded clauses into a single clause, using a(More)
The problem of rewriting a query using a materialized view is studied for a well known fragment of XPath that includes the following three constructs: wildcards, descendant edges and branches. In earlier work, determining the existence of a rewriting was shown to be coNP-hard, but no tight complexity bound was given. While it was argued that(More)
In this paper, we address a problem common in the frame of WWW, namely, representing information that assumes different facets under different contexts (sets of worlds). For expressing context-dependent (or multidimensional) data, we introduce Multidimensional Semistructured Data, where context is defined through (dimension, value) pairs. An extension of(More)
In this paper we address an issue common in the frame of WWW namely information entities that present di erent facets under di erent contexts or worlds Handling such multifacet or multidimen sional entities requires a multidimensional paradigm for Web data which consists of representation manipulation and presentation issues For rep resenting(More)
Metadata interoperability is an active research area, especially for cultural heritage collections, which consist of heterogeneous objects described by a variety of metadata schemas. In this paper we propose an ontology-based metadata interoperability approach, which exploits, in an optimal way, the semantics of metadata schemas. In particular, we propose(More)
Temporal and modal logics have been used in many applications in Arti cial Intelligence and Computer Science for the manipulation of information with time dependent or in general context dependent properties Knowledge representation and reasoning temporal planning simulation temporal veri cation and description of agent systems are among the applications(More)