Re: Bubo - Implementing OWL in rule-based systems

From: Jos De Roo (
Date: 12/03/02

  • Next message: Stefan Decker: "Re: Bubo - Implementing OWL in rule-based systems"
    Hi Stefan,
    this is a bit of a reply (while having holiday) to your nice paper
     > Three systems try to implement OWL using a LP-based approach:
     > The Euler Proof Mechanism [14] by Jos De Roo of Agfa and Tim
     > Berners-Lees Closed World Machine (CWM) [2] correspond very
     > closely and use the same syntactic format for rules. However both
     > do not consider data integration. They try to axiomatize everything,
     > whereas we try to rely on the features of logic itself, such
     > as implication to operationalize the transitivity of subclassof. Their
     > axiomatization is not proven to be correct or complete, e.g. they do
     > not capture the substituivity of sameIndividualAs and capture only
     > one direction of hasValue. There is no formaly proven characterization
     > of the inference algorithms employed by Euler and CWM.
     > So it is unclear what they are actually doing.
    really ;-)
    ok, w.r.t. owl:sameAs individuals they are found
    in a "prepare" method (running before the normal
    "proof" method) which is just quering for
       ?s owl:sameAs ?o.
    and then substituting individuals with an equivalent
    name (using a hashtable also keeping track of symmetry
    and transitivity)
    another point is that of existentials in consequents
    where we have a very clumsy way of handling the Skolem
    function terms (kind of trading trees attached to
    bnodes for function terms) but we now think that
    "being explicit" is much better
    take for example following data about 3 points in
    and assume that we also have as a premis
    (in there we have no Skolem functions in the
    consequents of the implications, just flat formulas)
    if we now want to know wether those 3 points are
    co-linear (*) within a certain tolerance, we ask
    and the answers are in
    and they both give
       :d43 a :CLDeviation.
    Jos De Roo, AGFA
    (*) a long time ago I constructed 5 wind mills
         but I failed to achieve appropriate
         co-linearity in the blades of rotor4
         and so it collapsed in a november storm...

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