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        <article-title>A Little Logic Goes a Long Way { Logical Reasoning in Web Data Integration and Ontology Learning</article-title>
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          <label>0</label>
          <institution>Universitat Mannheim</institution>
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      <p>There is an ongoing dispute in the Semantic Web Community about the
usefulness of (Description) Logic as a basis for describing data on the web. While
researchers in logic argue with the bene ts of logic in terms of a clean
semantics and richness of the language, criticism against the use of logic normally
focusses on two points: its computational complexity and its inability to
represent soft constraints. In this talk, we will address these criticisms and argue
that if used in the right way description logics are a valuable tool for typical
tasks on the semantic web. We use problem of semantic matchmaking as an
example to show that the use of rather inexpressive logics with good
computational properties already provide signi cant bene ts by eliminating incoherent
matches. In the second part of the talk we address the problem of dealing with
soft constraints and show two solutions to this problem that have proven
useful for matchmaking: Approximate subsumption as a purely logical framework
for partial matchmaking and Log-Linear Description Logics as a new
combination of Description Logics with (log-linear) probabilistic models. We show that
purely logical matchmaking achieves results comparable with state of the art
matchmaking systems that rely on similarity functions and present results that
show that log-linear description logics outperform existing matching systems.
We conclude that in the context of semantic web applications expressive power
of the logics used is less important than the integration with other formalisms
and technologies for improving e ciency and the ability to deal with imperfect
knowledge.</p>
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