Re: draft-kindberg-tag-uri

Dan Connolly writes:
> On Tue, 2002-10-29 at 13:35, Patrik Fältström wrote:
> > 
> > The IESG is to publish draft-kindberg-tag-uri as an informational RFC 
> > shortly. Comments on the draft is to be sent to me personally and the 
> > authors.
> 
> As I wrote to Sandro earlier...
> 
> I certainly don't agree with:
> 
> "But there are
>    drawbacks to URLs-as-identifiers:
> 
>    1) Software might try to dereference a URL-as-identifier, even though
>       there is no resource at the "location"."
> 
> (a) there's always a resource there; there might not be a representation
> available. But (b) if there isn't a representation available, there
> should be.

A year and a half ago, when we were drafting this, Tim Kindberg
phrased that text.  The phrasing grated a little on my W3C-trained ear
at the time, but I thought it spoke clearly enough to the wider
audience.  Let me try another phrasing:

     1) With many URI schemes (such as HTTP) there is no indication in
	the URI itself whether web content is available representing
	the identified thing; the availability of such content must be
	determined via metadata or experimentation.  While this
	flexibility can be very useful in some applications, in others
	designers may know in advance that for certain URIs such a
	representation will never be available.  When this is known,
	use of a tag URI avoids the need to communicate extra metadata
	or perform the web-retreival experiment.

Of course the text itself is really just informative, and could be
dropped with no change to the specification itself.

> i.e. names/identifiers take on meaning by use in protocols.
> I don't see much value for making up names without some
> sense of how they'll take on meaning.

By "take on" meaning, I assume you mean in the social sense of
establishing a meaning which is shared by various entities (as opposed
to simply having a meaning defined in private by a creator).  You're
right that tag URIs have no such associated mechanism.  We imagined
that in some cases, separation of these mechanisms could be
advantageous.

My imagined application was the Semantic Web with floating semantics:
the consensus meaning of an identifier is determined by considering
various documents using it, along with document metadata.  This
approach mirrors natural language; Tim Berners-Lee recently said it
should work in about fifty years; Pat Hayes said ten.

In proposing tags, I'm not saying when it might work, just that I'd
like people to be able to experiment as soon as they want to.

Our current work (you and I at W3C) is aimed at applications where
there *is* representative content available for retreival, and tags do
not support that approach.  Instead they support an alternative
approach which can co-exist peicefully.  In fact, if people want to
not publish initial authoritative semantics, then use of a tag URI
makes this clear; it means a system calculating the closure under
inclusion-of-origin-documents doesn't need to do a bunch of retreival
experiments.  (In RDF one could provide metadata saying no such
experiment will succeed, but that gives authors extra error-prone
work.  And what if the term creator wants to be sure no data is ever
taken as creator-authoritative?  Since triples can be freely dropped,
that information cannot be maintained.)

> And I don't see why the existing URI schemes don't work
> just fine for naming stuff.

There are people arguing that it is inappropriate to use each of the
other approaches in some circumstances.  Can you use an HTTP URI to
identify a dog?   Some say no.   Can you use an HTTP URI-Reference to
identify a dog?  Some say the dependence on media-type information
makes that also a bad idea; the naming is no longer uniform.

Tags at least get one clear of the controversy of retargetting
existing schemes.   They also get one clear of all the useful
machinery of the web, which is too bad.

I'm not saying which way we should go; I'm just saying we should have
tags so we can properly explore the territory.

> FYI, the W3C TAG has been doing work in this area; it's
> not finished, but a stake in the ground is:
> 
> "Describe resources: Owners of important resources (for example,
> Internet protocol parameters) SHOULD make available representations that
> describe the nature and purpose of those resources."
>   -- http://www.w3.org/TR/2002/WD-webarch-20020830/
> 
> >     Regards, Patrik
> >     Area Director, Applications Area, IETF
> -- 
> Dan Connolly, W3C http://www.w3.org/People/Connolly/

Sandro Hawke, W3C http://www.w3.org/People/Sandro/

Received on Wednesday, 30 October 2002 08:26:42 UTC