- From: Patrick Stickler <patrick.stickler@nokia.com>
- Date: Sun, 16 Jun 2002 14:52:51 +0300
- To: Pat Hayes <phayes@ai.uwf.edu>
- CC: RDF Core <w3c-rdfcore-wg@w3.org>
On 2002-06-14 19:41, "ext patrick hayes" <phayes@ai.uwf.edu> wrote: > ... Are you saying that when some > software reads some RDF, that it cannot possibly tell that > > http://www.w3.org/1999/02/22-rdf-syntax-ns#type > > is the symbol 'type' on the normative W3C website? In the context of RDF, a website has nothing to do with the interpretation of that term. If the application knows what "http://www.w3.org/1999/02/22-rdf-syntax-ns#type" means, then it knows how to interpret it. The fact that dereferencing that URIref via HTTP might result in retrieving some content has nothing whatsoever to do with the semantics it bears. And the relation that it might (or might not) have to some URIref that is a prefix of its own URIref string is also not relevant to the semantics it bears. All RDF employs is URIrefs, complete, opaque, unparsed. The percieved relationship between the URIref "http://www.w3.org/1999/02/22-rdf-syntax-ns#type" and "http://www.w3.org/1999/02/22-rdf-syntax-ns#" is residue from the XML serialization which has *no* semantic significance in the RDF graph whatsoever, insofar as the latter may have corresponded to a namespace prefix used in the construction of the former. Now, this is not to say that the term "http://www.w3.org/1999/02/22-rdf-syntax-ns#type" is not defined by an authoritative specification for the RDF Vocabulary (not namespace) owned by the W3C. And if it happens (by coincidence) that the RDF Vocabulary is denoted by "http://www.w3.org/1999/02/22-rdf-syntax-ns#" and for editorial convenience that same URIref was used as the XML Namespace prefix for serializing the term "http://www.w3.org/1999/02/22-rdf-syntax-ns#type" as an element or attribute name, that doesn't result in some formal relationship between those two URIrefs in the RDF graph based on the structural relation inherent in the qname. It is just a coincidence motivated by editorial convenience. Nothing more. This is why something line rdfs:isDefinedBy is required, if we wish to make the relationship between term and vocabulary explicit. There is, however, *never* a relationship between a term and a namespace, since namespaces are strictly a mechanism of the XML serialization and have no functional significance in the RDF graph. > You sure seem to > be saying that. I bow to your expertise, but it seems to me that if > this is true, then we are in much deeper doo-doo than anything to do > with dark triples. We are only in deep doo-doo *if* we force vocabularies to equate to XML Namespaces. So long as we (correctly) keep these two classes of entities distinct, and realize that there can be an N:1 relationship between XML namespace and vocabulary, and in fact that there can be an N:1 relationship between qname and URIref; and so long as we don't try to force XML qname structure and semantics onto RDF, we are just fine. URIs are the naming model for the web. RDF takes the web as its scope of focus. Qnames are the naming model for XML. Namespaces and qnames are strictly mechanisms of XML, which is simply one of many encodings used on the Web. RDF simply uses XML qnames to "tunnel" URIrefs between agents. RDF does not subscribe to the full structure and semantics of XML qnames (and in that regard is rather misbehaved) and it is meaningless to speak of 'namespaces' in the context of RDF graph semantics. Not only to namespaces not exist in the RDF graph, but even where there is the illusion of their existence, in RDF/XML it trully *is* an illusion because the qname is not carried forward into the graph but is "collapsed" into a URIref that discards any notion of a distinct namespace prefix. We simply need to stop thinking that XML Namespace equates to RDF Vocabulary. Sometimes they seem to coincide (mostly because it makes creating the RDF/XML easier) but they are simply not the same thing. >> <snip> >> Rather, the graph syntax should have an explicit mechanism >> that 'colors' triples as asserted or unasserted, > > No, it MUST NOT have such a mechanism. Any such mechanism in the > graph is inherently non-monotonic. This whole idea is a dead horse. Well, I'll bow to your expertise in that matter. I still don't see how "marking" a triple as dark based on "dark" predicates is any different from "marking" it as dark syntactically, but I guess it must be. Cheers, Patrick -- Patrick Stickler Phone: +358 50 483 9453 Senior Research Scientist Fax: +358 7180 35409 Nokia Research Center Email: patrick.stickler@nokia.com
Received on Sunday, 16 June 2002 07:48:37 UTC