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Knowledge Mediation in the WWW Based on Labelled DAGs with Attached Constraints.

Title:Knowledge Mediation in the WWW Based on Labelled DAGs with Attached Constraints.
Authors: J. Eusterbrock
Series:Linköping Electronic Articles in Computer and Information Science
ISSN 1401-9841
Issue:Vol. 6(2001): nr 007
URL: http://www.ep.liu.se/ea/cis/2001/007/

Abstract: This paper introduces a framework where the semantic access to Web resources is realised by a mediator module. Users can express their knowledge needs using the terms of a shared ontology without taking into account context-specific locations, encodings, and vocabulary. Integration among shared ontologies and Web meta data descriptions is achieved by inserting an intelligent meta-level layer using lifting rules. Lifting rules can be used to automatically decompose semantic information needs into concrete information requests. Wrapper and facilitator agents are used to find suitable information on the Web.

Labelled directed acyclic graphs (DAGs) allow a natural modelling of syntactical, structural and semantic properties of standardised XML Web data meta data, and ontologies, and their operations. However, graph-based data models are only a first step towards intelligent tools for automated knowledge extraction from the WWW. Planning and design synthesis of technical systems involve dealing with interacting constraints, imposed by selected tasks, such as cost or compatibility constraints, or general constraints.

As a step to cope with these requirements, a novel approach combining constraint processing and reasoning with Web (meta-)data is presented. Canonical graphterms are used for the encoding of labelled DAGs, which are embedded into constraint logic formulas, thus representing Web (meta-)data and ontologies. Graph rewriting and application of the built-in reasoning facilities such as matching, unification, subsumption and constraint solving of a constraint-logic language can then be used to efficiently automate mediation tasks.


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