web explanations for semantic heterogeneity discovery pavel shvaiko 2 nd european semantic web...
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Web Explanations for Semantic Heterogeneity Discovery
Web Explanations for Semantic Heterogeneity Discovery
Pavel Shvaiko
2nd European Semantic Web Conference (ESWC),
1 June 2005, Crete, Greece
work in collaboration with Fausto Giunchiglia, Paulo Pinheiro da Silva and
Deborah L. McGuinness
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Outline
Introduction
Semantic Matching
Inference Web (IW) Framework
Explaining Semantic Matching using IW
Experimental Study
Conclusions
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Introduction
Information sources (e.g., database schemas, classifications or ontologies) can be viewed as graph-like structures containing terms and their inter-relationships
Matching is one of the key operations for enabling the Semantic Web since it takes two graph-like structures and produces a mapping between the nodes of the graphs that correspond semantically to each other
Matching, however, requires explanations because mappings between terms are not always intuitively obvious to human users
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Semantic Matching
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Semantic Matching
Semantic Matching: Given two graphs G1 and G2, for any node n1i G1, find the strongest semantic relation R’ holding with node n2j G2
Computed R’s, listed in the decreasing binding strength order:
equivalence { = };
more general/specific { , };
disjointness { }
We compute semantic relations by analyzing the meaning (concepts, not labels) which is codified in the elements and the structures of schemas/classifications
Technically, labels at nodes written in natural language are translated into propositional logical formulas which explicitly codify the label’s intended meaning. This allows us to codify the matching problem into a propositional validity problem
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Example: Two simple classifications
?
=Cyberspace and Virtual Reality
Italy
Europe
Pictures
Images
Europe
ItalyTrento
Computers and Internet
D.E.
A1 A2
Axioms rel (Context1, Context2)
(Images1Pictures2) (Europe1Europe2) (Images1 Europe1) (Europe2 Pictures2)
Axioms Context1 Context2
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S-Match
Expl.
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Inference Web (IW) Framework
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The IW Framework Overview
Inference Web is a framework enabling applications to generate portable and distributed explanations for their answers
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Explaining Semantic Matching
using IW
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Producing Explanations
In order to explain mappings produced by S-Match and thereby increase the trust level of its users, we need to provide information about:
• background theories (e.g., WordNet)
• JSAT manipulations of propositional formulas
WordNet
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Default ExplanationA default explanation of mappings the S-Match system produces is a short, natural language, high-level explanation without any technical details. It is designed to be intuitive and understandable by ordinary users
Query: find "European pictures"
Query
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Explaining Background KnowledgeSuppose that the agent still does not trust the answer and may want to see the sources of metadata information behind the mapping
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Explaining Logical Reasoning
If the mappings derivation process needs to be explained, using the JSAT SAT engine, S-Match produces a trace of the DPLL procedure
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Experimental Study
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Preliminary Results
Goal: to obtain a vision of how the S-Match explanations potentially scale to requirements of the Semantic Web
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Conclusions
We use the Proof Mark-up Language for representing S-Match proofs, thus facilitating interoperability
We use meaningful terms rather than numbers in the DIMACS format, thus facilitating understandability
We use the IW tools, thus facilitating customizable, interactive proof and explanation presentation and abstraction
Our solution is potentially scalable to the Semantic Web requirements
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Future Work
Developing an environment, which efficiently exploits the IW proofs and explanations, in order to make the S-Match matching process (fully-fledged) interactive and iterative
Improving the S-Match proofs and explanations by using abstraction techniques more extensively
Conducting a user satisfaction study of the explanations
Extending explanations to other SAT engines as well as to other non-SAT DPLL-based inference engines
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References
Project website at DIT - ACCORD: http://www.dit.unitn.it/~accord/
Project website at KSL - IW: http://iw.stanford.edu/
F. Giunchiglia, P. Shvaiko: Semantic matching. The Knowledge Engineering Review Journal, 18(3):265-280, 2003.
F. Giunchiglia, P. Shvaiko, M. Yatskevich: S-Match: an algorithm and an implementation of semantic matching. In Proceedings of ESWS, pages 61-75, 2004.
D. McGuinness, P. Pinheiro da Silva: Explaining Answers from the Semantic Web: The Inference Web Approach. Journal of Web Semantics, 1(4): 397- 413, 2004.
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Thank you!