Re: Mistaken identity?

Jon Hanna wrote:

> I read that as good separation between specs.
> 1. URIs provide a way to identify resources.
> 2. HTTP provides a way to GET or PUT representations of resources, or POST
> represetations into them.
> 3. RDF provides a way to describe relationships between resources identified by
> URIs, or between resources and literals.

Well, 1) and 3) go together nicely.  It's just 2) that is the odd man 
out.  A lot of people would like to have a retrievable URI denote the 
thing that gets retrieved, or at least the resource of which the 
retrieved thing is a representation.  Trouble is, it leads to so many 
problems that no one has convinced many others that they know how to 
make it work.

For example, given a retrievable URI -

A. Does it denote i) the URI string itself, ii) the resource whose 
representation gets retrieved, or iii) one of the representations (and 
if so, which one?)?

B. If you picked ii) or iii), how do you talk about the URI string itself?

C. How do you know which URIs are supposed to be treated one way - as 
denoting the resource they point to - and which the other, given that 
actual sites go up and down, change, domains get bought and sold, etc.?

D. If you picked A.ii or A.iii, what is supposed to happen when the 
resource itself changes its state, which may mean gets completely 
changed or replaced?

These are not trivial questions to answer.  Maybe we will eventually get 
a convergence on a solid and reliable convention about the issue, but 
until we do, what can we do except to go along with what the current RDF 
Rec(s) say?

> That HTTP, RDF and indeed RDS don't have anything to say about each other is
> dulce et decorum; but they both depend on the use of URIs to identify resources
> and when a URI is used in both HTTP and RDF then it sould identify the same
> resource (or it's a pretty lousy identifier, not an identifier at all really).

&rdf;type and &rdfs;label seem like pretty good identifiers to me, and 
they don't have to be retrievable - and if they were, they would not 
denote the retrieved thing.


Tom P

Thomas B. Passin
Explorer's Guide to the Semantic Web (Manning Books)

Received on Wednesday, 23 June 2004 19:18:33 UTC