- From: pat hayes <phayes@ihmc.us>
- Date: Mon, 21 Jul 2003 17:25:57 -0500
- To: "Williams, Stuart" <skw@hp.com>
- Cc: www-tag@w3.org
> > -----Original Message----- >> From: pat hayes [mailto:phayes@ihmc.us] >> Sent: 19 July 2003 19:42 >> To: Williams, Stuart >> Cc: www-tag@w3.org >> Subject: RE: resources and URIs >> >> >> >Tim (or Pat), >> >> No, that would be illegal by my way of thinking. >> >> http://chandra.harvard.edu/NGC/ngc1068 is an information resource. >> >> You would expect >> >> >> >> >> >> <rdf:Description >> rdf:about="http://chandra.harvard.edu/NGC#ngc1068" >> >> rdf:type="http://chandra.harvard.edu/AOtype/Activegalaxy7" >> >> </rdf:Description> >> >> >> >> or, in the http://chandra.harvard.edu/NGC information ressource,, >> >> >> >> <rdf:Description >> >> rdf:about="#ngc1068" >> >> rdf:type="http://chandra.harvard.edu/AOtype/Activegalaxy7" >> >> </rdf:Description> >> >> >> >> where you can see that local identifiers can be used to refer to >> >> abstract things, because that is what the RDF language spec says. >> > >> >Can you provide a reference to what the RDF language spec actually says >> >on this topic, I'd like to read it for myself. >> >> The relevant citation is probably >> >http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-concepts-20030117/#section-fragI >D > >Ok... thanks. > >What I am really looking for is the source of a probibition on using http: >scheme URI (without fragment Ids) to denote real-world things and abstract >concepts. There is none in the current spec. >Tim uses the strong word 'illegal' above. I continue to fail to >understand why he feels so strongly that this is illegal. Er,... because he wants it to be? But to be more charitable, it does kind of make sense given the common useage of things like rdfs:subClassOf, since one can say that the bare URI there ought to denote the document containing the 'definition', since such bare URIs are used for that purpose in the OWL 'imports' assertions to refer to ontologies. In fact, on reflection, that might be a better citation, eg see http://www.w3.org/TR/owl-guide/#OntologyVersioning On the other hand, the semantics of 'imports' is tricky to get right and not yet fully articulated; and it seems risky to impose a condition which depends on such a shaky foundation as fragIds and which already has large-scale deployed code in violation. My own view is that there really is no real *need* for this kind of a ruling, and that to try to impose it on the entire Web is like, to use a fine old expression, pissing into the wind. BTW, a weaker ruling could be that any 'bare' HTTP URI ending in ".owl" should be taken to denote an OWL ontology. That is sufficient to carry the burden of OWL importing while freeing up other URIs to denote whatever anyone wants them to. Or, we could just say that the semantics of 'owl:imports' is such that if you try to import anything that is not an OWL ontology then nothing happens, which makes it a purely OWL internal matter, which seems tidier to me. >His appeal to >"what the RDF language spec says." appeared to be in support of the claim of >illegality. What the RDF spec says is that URI refs with frag ids CAN be >used for this purpose (denoting the thing described by some fragment in an >RDF document) BUT it does not 'outlaw' the use of URI refs without frag ids >(and particlarly http: URI without frag ids) for the same purpose - as in >your original RDF fragment, or the 2nd fragment above which 'illegally' uses >an unfragmented URI to denote an RDF class. True. > >This is the substance of httpRange-14 [1]. I think that this is tangled up >in the distinction this thread has been discussing of an information >resource (ie. a source of representations) and the thing the representation >is some sense about (ie. the weather in Oaxaca or a 'galaxy far far away'). > >BTW had you consider the effects of placing a super-massive black hole >'on-the-web' or at least in close proximity to it :-) Yes. Hey, for all we know we may already be inside an event horizon. > >[1] http://www.w3.org/2001/tag/ilist#httpRange-14 > > >> >>I was under there impression that RDF gave URI References (2396 > > >>terminology) an entirely opaque treatment. >> >> The semantics treats them completely opaquely: however, existing >> RDF/DAML/OWL *practice* seems to often follow the convention outlined >> by Tim, where a URIref of the form ex:place#thing denotes an entity >> described by some RDF which can be found at the address ex:place. > >A common practice or convention, yes, but what makes it so essential as to >regard other practices/conventions as illegal? Im probably the wrong person to ask :-) Pat -- --------------------------------------------------------------------- IHMC (850)434 8903 or (650)494 3973 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32501 (850)291 0667 cell phayes@ihmc.us http://www.ihmc.us/users/phayes
Received on Monday, 21 July 2003 18:26:00 UTC