- From: Pat Hayes <phayes@ihmc.us>
- Date: Mon, 18 Apr 2011 13:02:35 -0500
- To: Ivan Herman <ivan@w3.org>
- Cc: Pierre-Antoine Champin <pierre-antoine.champin@liris.cnrs.fr>, RDF Working Group WG <public-rdf-wg@w3.org>
On Apr 18, 2011, at 8:16 AM, Ivan Herman wrote: > > On Apr 18, 2011, at 15:00 , Pierre-Antoine Champin wrote: > > <snip/> >>>> Not so easy. When you *use* a URI in RDF, like the <g> here, it is >>>> not referring to itself, but to what it denotes. (Put another way, >>>> the URI is not quoted.) Which means that rdf:tags isn't going to >>>> have the meaning you intend. Now, we could change this, and say >>>> that rdf:tag is (uniquely) referentially opaque in its subject >>>> position. This would however be a major change to the RDF semantics >>>> and data model, and would require us to re-wrote the semantic spec. >>>> And it has other knock-on consequences eg for OWL, since OWL >>>> equality reasoning would have to be blocked from such triples. So I >>>> think we should think very hard before going there. >>>> >>>> However, XML Schema has a datatype for making literals refer to >>>> URIs. http://www.w3.org/TR/xmlschema-2/#anyURI and we could use >>>> that. OK, we can't have a literal in subject position (sigh), so we >>>> have to turn it around: >>>> >>>> <h> rdf:taggedBy xsd:anyURI^^"<the URI written as a string>" . >>>> >>>> and then it would all work, without breaking the RDF semantics. >>> >>> I understand, but isn't this problem a reflection of the fact that we >>> try to model here the common term of tagging, ie, attaching a string >>> to a resource as some sort of a characterization of the latter? In >>> fact, as we said at the f2f, SPARQL is blissfully silent on how that >>> URI is used. If we want to avoid misunderstandings through the usage >>> of the word tagging, we can say something like >>> >>> <g> rdf:loose_association_of_resources <h> . >> >> nah... >> >> <i> owl:sameAs <g> . >> >> entails >> >> <i> rdf:loose_assoctiation_of_resources <h> . >> >> Is this what you want to say?? > > Hm. I do not know... > > Given that SPARQL is loose in the way they use URI-s from graphs in datasets, I would not be shocked by this. The question is what would the SPARQL 1.1 entailment regime say about this. > > But, again: I wonder whether we have to say anything in formal terms at all about SPARQL's behaviour, except to make it clear that (<g>,G) is _not_ a shorthand for <g> identifying G. But, Ivan, this thread began when *you* suggested using RDF to assert/declare something about SPARQL behavior. Which is exactly what is ruled out by this looseness. All Pierre-Antoine and I are doing is trying to take your idea and make it work in RDF. Are you now saying it was a bad idea all along, or are you saying that we don't need to do it using RDF, or what? Pat > > Ivan > > >> >> I prefer Pat's proposa: if you want to associate something with a *uri* >> (and not a resource), use a xsd:anyURI literal. >> >> pa >> > > ---- > Ivan Herman, W3C Semantic Web Activity Lead > Home: http://www.w3.org/People/Ivan/ > mobile: +31-641044153 > PGP Key: http://www.ivan-herman.net/pgpkey.html > FOAF: http://www.ivan-herman.net/foaf.rdf > > > > > ------------------------------------------------------------ IHMC (850)434 8903 or (650)494 3973 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 mobile phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
Received on Monday, 18 April 2011 18:03:07 UTC