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Re: Section 2: What does a URI identify? (and range of HTTP deref)

From: Sean B. Palmer <sean@mysterylights.com>
Date: Wed, 27 Mar 2002 13:19:23 -0000
Message-ID: <008b01c1d592$0610f280$ceb90150@localhost>
To: "Tim Bray" <tbray@textuality.com>
Cc: <www-tag@w3.org>
> [...] It seems that there is a hierarchy of resource classes
> in here, whether or not we have the language to talk about

The problem with the genericity hierarchy is that it's very
difficult to put a boundary on what constitutes a "document"
exactly (Class C in your hierarchy). Dan Brickley has raised this
concern with the model already on www-rdf-interest:-

The distinction is only useful if it can be defined clearly
enough to implement to. Is a Web Service a document? (CGI-based,
SOAP etc) An image? What about a mailbox (eg. could http: URIs
name the same things as mailto: URIs)? What about Shakespeare's
"Hamlet", abstractly conceived, is that a document? [...]
]]] -

This is a huge argument, and it's been going on for quite some
time. The practical dilemma that this whole issue raises, for me,
is whether to end my namespace names (in RDF) with a hash or a
slash. IMO, HTTP URIs and URI-references can refer to any
"resource" per the definition in RFC 2396. As DanC pointed out,
this is the minimally constraining scenario.

> [...] Finally, is there anything in the space between class A
> class C resources?  Maybe.

Personally, I think that this way lies madness. In fact, I've
spontaneously used the same words that Michael Mealling used in
reply to Patrick Stickler's URI hierarchy proposal on the
URN-IETF mailing list:-

Being one of the people in the URI-IG that discussed the
classical vs contemporay view (and an adherent of the
contemporary view) I have to say that this way lies madness.
[...] The thing that has become clear is that a given URI's
characteristics have more to do with how it is used than what its
scheme says. For example, Dan uses the http scheme for pretty
much everything. For him the http scheme makes a pretty valid
urn-like thing.
]]] -

So even if in the context of your day to day business you hold
the view that an HTTP URI can only identify a documentish or
pseudo-documentish thing (classes C and B), others might not, and
they can express that fact using RDF/HTTP headers etc. Since the
"identify anything" view is the most liberal, it's best to
implement to that, IMO.

Kindest Regards,
Sean B. Palmer
@prefix : <http://purl.org/net/swn#> .
:Sean :homepage <http://purl.org/net/sbp/> .
Received on Wednesday, 27 March 2002 08:20:05 UTC

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