- From: Dan Connolly <connolly@w3.org>
- Date: Fri, 11 Nov 2005 09:40:32 -0600
- To: Eric Prud'hommeaux <eric@w3.org>
- Cc: public-rdf-dawg@w3.org
On Fri, 2005-11-11 at 09:52 -0500, Eric Prud'hommeaux wrote: > I took a while to get back to this as I was on vacation. Apologies. > > On Sun, Oct 30, 2005 at 08:18:44AM -0600, Dan Connolly wrote: > > > > On Sun, 2005-10-30 at 04:59 -0500, Eric Prud'hommeaux wrote: > > > SPARQL differentiates between IRIs, Literals and Blank Nodes. A term > > > for IRI shows up in the definition of the isIRI test. STR, as well the > > > return type of DATATYPE. Originally, I used terms like "RDF URI" and > > > "RDF literal" to define the semantics and return types of functions. > > > At some point, I thought it would be a good idea to switch to > > > rdfs:Resource and rdfs:Literal. But rdf:Resource is EVERYTHING, so I > > > needed another term. > > > > > > DanC suggested xsd:anyURI. This promotes all strings of type > > > xsd:anyURI to RDF resource. > > > > Everything is an RDF resource. So there's no "promotion". > > AGG! We need 2 different terms here. There are things that the RDF > Model calls URIrefs, and there are resources: > > Resources > / | \ > URIrefs literals bNodes Yes, that's an accurate picture, where the lines represent rdfs:subClassOf. Note that the term "URIref" is obsolete in favor of IRI. SPARQL is defined in terms of IRIs. > We specifically need a name for URIrefs because it: > 1. is the return type of DATATYPE() yes, xsdt:anyURI works well there. > 2. defines the semantics of isIRI() well, isIRI is a function of *terms*, not what the terms denote. It doesn't really depend on what URI we use for the class of URIrefs/IRIS. > 3. defines the semantics of STR() I don't see any connection to STR(). > > > For instance, if I write some XML: > > > <foo bar="4" baz="http://www.w3.org/"/> > > > , validate it by some W3C XML Schema: > > > <xs:element name="foo"> > > > <xs:complexType> > > > <xs:attribute name="bar" type="xs:integer"/> > > > <xs:attribute name="baz" type="xs:anyURI"/> > > > and write out the PSVI as RDF, I am making an assertion about the > > > resource <http://www.w3.org/> (didn't look up the *real* PSVI > > > projection in to RDF here): > > > [ a Element; > > > hasAttribute [ > > > name "bar", > > > value 4 ] , > > > hasAttribute [ > > > name "baz", > > > value <http://www.w3.org/> ] ] > > > > no, it would be: value "http://www.w3.org/" > > I can imagine justifications for either <http://www.w3.org/> or > "http://www.w3.org/"^^xsd:anyURI , but "http://www.w3.org/" makes > no sense at all to me. Why does the thing with the lexical form "4" > and the type xs:integer turn into an integer, but the thing with > the lexical form "http://www.w3.org/" and the type xsd:anyURI not > turn into at least one of those? OK, "http://www.w3.org/"^^xsd:anyURI . I didn't catch the subtlety of the value property; I thought it gave the/a lexical representation. I read too quickly. > > > However, this approach require a couple exceptions that I'm not > > > comfortable with: > > > > > > In general, datatypes can be transformed with > > > STR: > > > STR("asdf"^^foo:bar) = "asdf" > > > DATATYPE: > > > DATATYPE("asdf"^^foo:bar) = foo:bar > > > and ^^ casting: > > > "asdf"^^xsd:integer = "asdf"^^xsd:integer > > > > > > This (I believe, though this merits a test case) holds for SPARLE terms: > > > STR(4) = "4" > > > DATATYPE(4) = xsd:integer > > > "4"^^xsd:integer = 4 > > > > > > Some of these functions still work for URIs: > > > STR(<http://www.w3.org/>) = "http://www.w3.org/" > > > and maybe DATA > > > DATATYPE(<http://www.w3.org/>) = xsd:anyURI > > > > no; the datatype of W3C's homepage isn't xsd:anyURI. Use/mention bug. > > > > The xsd:anyURI datatype works just like all the others: > > "just like"? > I don't think you're arguing constructively here. We need to figure > out exactly what you think xsd:anyURI is. I think it's what the W3C XML Schema recommendation says it is. > Either you are conflating > two nodes that are distinct in RDF semantics: > the URIref <http://www.w3.org/> > the typed literal "http://www.w3.org/"^^xsd:anyURI > or you are saying that > the typed literal "http://www.w3.org/"^^xsd:anyURI > doesn't exist, or you are saying that SPARQL does not allow you to > distinguish the difference. > DATATYPE(<http://www.w3.org/>) = DATATYPE("http://www.w3.org/") Indeed, SPARQL doesn't assign any meaning to DATATYPE(<http://www.w3.org/>) and hence doesn't really allow you to distinguish the difference between DATATYPE(<http://www.w3.org/>) and anything else. > > DATATYPE("http://www.w3.org/"^^xsd:anyURI) = xsd:anyURI > > and > > str("http://www.w3.org/"^^xsd:anyURI) = "http://www.w3.org/" > > > > but we don't really "know" the lexical form for URIs > > > > We know the lexical form for URI literals. URI literals > > are self-denoting;t hey work differently from <xyz> symbols. > > > > > so > > > "http://www.w3.org/"^^xsd:anyURI != <http://www.w3.org/> > > > > > > > > > I don't think it's a good idea to invent a term or syntax for this, so > > > I'm in favor of going back to a term that's not a URI (RDF Resource). > > > > Which do you mean? URI or Resource? Remember, _everything_ is a > > resource. > > URIref xsd:anyURI is the W3C Recommended URI for the class/datatype of IRIs. (well, the class is actually a bit larger; it includes relative URI/IRI references too. But it's close enough for our purposes.) > > > There is a precedent for this in SPARQL ("RDF term", "blank node") and > > > in XPath Functions and Operators ("numeric"). > > > > > > > > > I'm on vacation this week in Italy. I'd like to resolve this when I > > > get back. > > > > What is it that you'd like to resolve? > > > > > > > > > > > Earlier thread: > > > http://www.w3.org/mid/20050911103218.GF17622@w3.org > -- Dan Connolly, W3C http://www.w3.org/People/Connolly/ D3C2 887B 0F92 6005 C541 0875 0F91 96DE 6E52 C29E
Received on Friday, 11 November 2005 15:40:38 UTC