Re: Valid representations, canonical representations, and what the SW needs from the Web...

Sandro Hawke wrote:
>...
> 
> The URI part of an RDF URIRef has no special status in RDF.  It is
> explicitely not the address of a schema or such.  I argued it should
> be and lost.

Are you saying that it is illegal for a UA to dereference a URIRef 
looking for a schema?

If so, then you are right, it is totally silly that RDF uses URIs as 
tokens (except for purposes of describing web resources).

> Tag: identifiers are no more dereferncable than than UUIDs.
> 
> In all three cases (http, tag, uuid) you have to find your schema (or
> whatever) via extra triples (rdfs:isDefinedBy or owl:imports in the
> instance data), or some out of band approach (eg google).  
> 
> Oh, maybe if you use a non-fragmwnt URI (like dc: and foaf: ) , then
> http GET would be sanctioned.   You imagine http GET on dc:title
> should get you the schema?

I'm confused. dc:title is a short-form for 
{"http://purl.org/dc/elements/1.1/", "title"}

If I do a GET on "http://purl.org/dc/elements/1.1/" I _do get_ a schema. 
Today.

>...
> This is about the social meaning of uris, about people agreeing on
> what a uri/symbol means.    Isn't it easier to agree on the observable
> qualities of a URI than tose which are by definition in someone's
> head?

I don't know what you are saying. As Roy said, a URI has an associated 
contract (just as a function or class in a programming language does). I 
presume that "http://www.w3.org/Markup" will have information about HTML 
by the W3C. But the W3C has never said that anywhere explicitly so the 
contract is inferred. And they have especially never said that I should 
use that URI to represent HTML in semantic web contexts. So in my 
opinion, it would be a REALLY BAD IDEA to reuse that URI as a universal 
name for "HTML". On the other hand, if the W3C makes an RDF document and 
assigns it a URI and says: "Use this whenever you want to talk about 
HTML" then I have an explicit contract (like the type signature or 
comments in a programming language). The "/Markup" page isn't "wasted". 
It was never intended to be used to mean "HTML" in the semantic web and 
it has no business being used that way.

  Paul Prescod