- From: Jan Grant <Jan.Grant@bristol.ac.uk>
- Date: Tue, 25 Jun 2002 11:07:05 +0100 (BST)
- To: patrick hayes <phayes@ai.uwf.edu>
- cc: w3c-rdfcore-wg@w3.org
On Mon, 24 Jun 2002, patrick hayes wrote: > > >Pat indicated at the F2F that entailments "accidentally" drawn would be > >"harmless". > > RDF entailments, yes. > > >Can someone clear up this example for me? > > > >A: > > <eg:foo1> <rdf:subPropertyOf> <dark:eg:foo2> . > > <dark:eg:foo2> <rdf:subProperotyOf> <eg:foo3> . > > > > <eg:a> <eg:foo1> <eg:b> . > > > >B: > > <eg:foo1> <rdf:subPropertyOf> <dark:eg:foo2> . > > <dark:eg:foo2> <rdf:subProperotyOf> <eg:foo3> . > > > > <eg:a> <dark:eg:foo2> <eg:b> . > > > >C: > > <eg:foo1> <rdf:subPropertyOf> <dark:eg:foo2> . > > <dark:eg:foo2> <rdf:subProperotyOf> <eg:foo3> . > > > > <eg:a> <eg:foo3> <eg:b> . > > > > > >Does A |= C? Does A |= B? B |= C? > > Yes: > A|= C (by subproperty chaining and then the subproperty closure rule) > No: > A |= B (dark conclusion) Actually, for the same reason, isn't this a "yes"? Because the non-dark statements are a strict subset of the antecedent? > B |= C (dark, ie missing, antecedent) > > However, notice that should be rdfs:subPropertyOf. To anticipate your > next question: yes, one does have to be careful using darkened > triples in RDFS hierarchical inferences (basically, any kind of > transitivity implication, ie subPropertyOf and subClassOf.) What I > claimed was that it was safe with RDF-valid reasoning (ie > effectively, existential generalization). To be honest, I think examples like this are why we should have an explicit, not implicit name-based, darkening mechanism. At the F2F I was in favour of it, but the more I think about it the more it seems like a mistake to key this off property names. Some explicit syntax mechanism (either Patrick's, or an "rdf:asserted='True'" or such) seems much less error-prone... particularly if we can provide a little more sugar by having shorthand constructs (daml:collection) that normally produce some darkened triples do that "by default". jan -- jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/ Tel +44(0)117 9287088 Fax +44 (0)117 9287112 RFC822 jan.grant@bris.ac.uk and Nostradamus never dreamed of the Church of the Accellerated Worm
Received on Tuesday, 25 June 2002 06:09:43 UTC