Re: namespace usage as assertions

Rick JELLIFFE wrote:
> 
> Dan wondered why he has to explain resources so many times. Perhaps this
> exchange is informative:
> 
> > From: Dan Connolly (connolly@w3.org)
> 
> > "Manola,Frank A." wrote:
> 
> > > To wit:  isn't it the case at the moment that, since the URIs that
> > > identify namespaces may actually point to nothing,
> >
> > That's not the case. Every URI, by definition, identifies/points to a
> > resource.
> ...
> > In particular, if the user chose a namespace name beginning
> > with http:, you can infer that a description of/representation of
> > the resource identified by that URI is generally available on demand.
> 
> Here, when Mr Manola uses "actually" I read it as meaning "ultimately".
> But Dan takes it as meaning "proximately".
> 
> In typical computer languages, we are used to a left-hand side and a
> right-hand-side of an assigment or equation operator. There is a name on
> the left, and an evaluatable value on the right (unless you are using
> BLISS). If URIs could be explained in terms where "resource" does not
> seem to sometimes be used for the LHS (the identifier?) sometimes for
> the LHS (the entity?) and sometimes for the = (retrieval semantics?
> referencing semantics?)  I am sure many people would find it helpful.

You might try the following work in progress

State and Storage: Files, Documents, and Resources 
http://www.w3.org/Architecture/state
Dan Connolly
$Revision: 1.32 $
$Date: 1999/09/17 21:28:26 $ $Author: connolly $ 

including

	"The relationship between URIs, resources, and content is similar to
the
	relationship between identifiers, variables, and values in a program:
it
	depends on the state of the program. But the Web is a distributed,
	parallel computation, not a sequential program. Its state is exposed in
	messages between agents [...]"

> The thing I find difficult is that "resource" seems to mean "anything
> that has a URI" but that the property of having a name, and the essense
> of having being because of having a name is pretty tenuous. It is too
> thin a definition not to be confusing: indeed it seems almost vapid. If
> the only property that brings a resource into being is having a name,
> then why make the distinction between (absolute) names and resources?

I think because it is the traditional way that
identifiers/symbols/addresses/names are discussed... the Web
is a communication medium, and it involves a fairly conventional
use of messages (documents) involving symbols (URIs) that
have referents (resources).

And because it's a reasonable model of how people intuitively understand
the Web: you're happy for your web browser to color links
to http://www.w3.org/ purple, i.e. you'd agree you've visited
what that identifier points to, even though you haven't seen
the latest version of the entity currently available there.

But I agree that it is tenuous; my
"State and Storage: Files, Documents, and Resources " article
also says:

"To model state distribution in the Web mathematically, we take as
axiomatic that URIs are unambiguous, i.e. each URI refers to exactly
one resource (c.f. sameness in Axioms of Web architecture). We leave
the issue of resource identity in the informal realm of philosophy; only
URIs occur in this formal mode. "

Perhaps I should take a break from this email discussion and
finish the article and the larch formal description that goes with it...

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/

Received on Wednesday, 21 June 2000 16:52:22 UTC