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

Received on Tuesday, 4 February 2003 14:10:29 UTC