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Re: ISSUE-58: Scalability of URI Access to Resources

From: Chimezie Ogbuji <chimezie@gmail.com>
Date: Wed, 22 Aug 2007 17:26:55 -0400
Message-ID: <f6ec8dcb0708221426i5b3f3952td546b8c5393d7f36@mail.gmail.com>
To: www-tag@w3.org

Pat, thanks for calling out this overlap with the ongoing discussion.
One point of clarification is *all* the discussion in that particular
thread has to do with RDF URIs specifically.  The difference may be a
little more than subtle, considering ISSUE-58 and the URNs Namesapces
and Registries finding address URIs in general and not URIs in RDF
specifically .

The concerns (as I see it) have more to do with automated machine
interaction and not human interation.  It dips into both the URNs
Namespaces and Registries finding as well as with ISSUE-58.  The key
point which links the two is the suggestion that (even when used
within RDF graphs) HTTP URIs should be preferred generally.  Below are
my comments to Norm's response:

1. http: != dereference

Yes, this is very clearly stated in the URNs Namespaces and Registries
finding.  However, we cannot have our cake and eat it too.
Specifically, there seems to be a bit of a conflict with: 1) The
prominent suggestion that HTTP URIs should be used pervasively, 2) The
equally prominent suggestion that it is a good idea to provide
representations for these URIs, 3) ISSUE-58 and 4) The 'qualifier'
above that the use of the HTTP scheme does not mandate dereference.

As Noah suggests, the qualifier can be interpreted by the author as a
suggestion that providing representations is not necessary.  In
addition, it can be interpreted by the consumer as a suggestion to not
bother attempting to (arbitrarily) dereference these URIs (many
don't).  If a little bit of ambiguity was the only price being paid,
it wouldn't be much of a concern, however, ISSUE-58 clearly identifies
the cost as much more than ambiguity alone.

I believe the appropriate recommendation, guideline, etc.. would be
one which includes a clearly articulated set of scenarios which
demonstrate when 'arbitrary' HTTP dereference (though not mandated) is
useful for automatons/agents and when it might not be so useful (XML
namespaces, for example).

2. The dereference problem is scheme independent

The second part of this particular point assumes there will
*inevitabely* be a need to dereference these (insert your favorite
other scheme here) URIs.  This is not always true, especially when the
URIs in question are RDF URIs.  RDF URIs and their use have a
model-theoretic mechanism for making claims about the world.  In most
cases, these claims (very mathematical in nature) are meant to be much
more authoritative than what representation you might get from
dereferencing the URIs themselves especially when the claims are
subject to much more fine-grained constraints through the use of a
formal (OWL) ontology.

The only caveat might be where the representations retrieved describe
the very OWL ontologies which capture these constraints.  In this
case, and with ISSUE-58, as a backdrop it would seem prudent to review
current practice in this regard or (perhaps) suggest some best
practices.  However, again this is specific to RDF and ISSUE-58
applies to all usage of URIs.  RDF URIs have a different usage pattern
than the typical Web scenario and the literature should consider this
divergence.

In addition, the dereference problem is not entirely scheme
independent.  Actually, it *only* applies to those URI schemes which
are (formally) associated with a transport protocol (ironically, the
same scheme(s) which are the subject of suggestion for their pervasive
use).

-- Chimezie
Received on Wednesday, 22 August 2007 21:27:03 GMT

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