Softlution WebTechnology GmbH,
J Eusterbrock Mediation Based on Labelled DAGs with Attached Constraints
Labelled directed acyclic graphs (DAGs) allow a natural modelling of syntactical, structural and semantic properties of XML Web data, DTDs, and ontologies, and their operations. However, such formal models are only a first step towards knowledge extraction from the WWW for building intelligent applications. Planning or design synthesis of technical systems involves reasoning with interacting constraints, imposed by selected tasks, such as cost or compatibility constraints, or general constraints. This paper introduces a combined framework for the declarative representation of Web meta-data and attached constraints. It uses canonical graphterms for the encoding of labelled DAGs, which are embedded into constraint logic formulas. 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. Integration is achieved by inserting an intelligent meta-level layer using lifting rules, wrappers and facilitators. Users can express their knowledge needs using the terms of a shared ontology without taking into account context-specific locations, encodings, and vocabulary.