- From: Dan Connolly <connolly@w3.org>
- Date: 28 Feb 2002 13:49:12 -0600
- To: Pat Hayes <phayes@ai.uwf.edu>
- Cc: w3c-rdfcore-wg@w3.org
On Wed, 2002-02-27 at 17:05, Pat Hayes wrote: [...] > At present, a graph entails its existential generalization which is > gotten by 'erasing' urirefs into bnodes, eg > > ex:Jenny ex:age what:ever . |= ex:Jenny ex:age _:x . > > Do we want this to be true for literals as well? Eg should this be a > valid inference? > > ex:Judy ex:age "10" . |= ex:Judy ex:age _:x . yes. It is in our "swap" software. I can make test cases if anybody likes. > It seems to me that we should do this, since there is no doubt that > literals do denote something - themselves, in fact - in any > interpretation. > > This means that the following inference would be valid, for example: > > ex:Jenny ex:age "10" . |= ex:Jenny ex:age _:y . > > which might seem a bit worrying if there was an rdfs:drange assertion > around, eg > ex:age rdfs:drange xsd:number > which imposes the 'lexical' datatype in the first case, but looks > like it might impose the 'value' in the second case; but in fact it > is OK, since that conclusion would only trigger the value datatyping > constraint if the bnode were also the subject of rdfs:dlex; and that > in turn would require the original graph to have had something like > this in it: > > ex:Jenny ex:age "10" . > "10" rdfs:dlex "12" . > > which is so crazy that no-one should be surprised if it has crazy > entailments, right? right. > Anyway, if y'all agree that we should accept this inference, then I > think the simplest way to re-do the MT is to simply say up-front that > *all* RDF interpretations must include *all* literals in their > universe. yup; that seems straightforward. > Then we can just say that for literals E, I(E) = E, and not > talk about things like LV and XL at all. Does anyone have any > philosophical objections to this? It would allow quite a few of the > lemmas to be stated with fewer qualifications, and the proofs to be > simplified. > > Pat > -- Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 28 February 2002 14:49:14 UTC