From: Jos De Roo (firstname.lastname@example.org)
Hi Stefan, this is a bit of a reply (while having holiday) to your nice paper http://www.daml.org/listarchive/joint-committee/att-1254/01-bubo.pdf ... > Three systems try to implement OWL using a LP-based approach: > The Euler Proof Mechanism  by Jos De Roo of Agfa and Tim > Berners-Lees Closed World Machine (CWM)  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 -- http://users.skynet.be/jdroo/2002/12cl/clD.n3 and assume that we also have as a premis -- http://users.skynet.be/jdroo/2002/12cl/clP.n3 (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 http://users.skynet.be/jdroo/2002/12cl/clC.n3 and the answers are in -- http://users.skynet.be/jdroo/2002/12cl/clT.n3 -- http://users.skynet.be/jdroo/2002/12cl/clE.n3 and they both give :d43 a :CLDeviation. -- Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/ (*) a long time ago I constructed 5 wind mills -- http://users.skynet.be/jdroo/rotor.html 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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