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URI concerns continue

• From: "Simon St.Laurent" <simonstl@s...>
• To: XML-Dev Mailing list <xml-dev@x...>
• Date: Mon, 10 Jul 2000 10:40:08 -0400

I (desperately) don't want to rehash the past 1700+ messages on xml-uri,
but I'm concerned that the 'URIs in namespaces' issues seem to be spreading
to XLink and to some extent to schemas.

The 'solution' [1] put forward to answer the battle over relative URI
references in namespaces should free lots of specifications from the
current logjam, though it isn't clear [2] that the solution actually solves
the problem so much as avoids it.

Last week's XLink Candidate Recommendation [3] seems to bring the same
questions that puzzled the xml-uri mailing list into a new venue, without
providing any more specific answers.  As Eric van der Vlist noted [4],
questions regarding how to compare URI-based role and arcrole attributes
are left unanswered, as is the pesky question of whether relative URIs are
acceptable in these 'semantic attributes' and how they should be treated.
(Plus there's always the lurking question of what if anything should be
done with the entity bodies that may or may not be identified by these
URIs.)  It's also not clear that the 'solution' for namespaces URI
references is appropriate to XLink URI references.

Saturday, I put up a proposal on xml-uri [5] suggesting that the W3C stop
using URI references unless questions of comparison and processing are
explicitly answered, either on a spec-by-spec basis, or in a general
Recommendation.  So far, I haven't seen any public response.

Today, on xmlschema-dev, we've had a brief run of questions regarding how
to to identify local copies of a schema when the Internet is unavailable
[6].  My suggestion that something akin to PUBLIC identifiers be used to
make such problems more manageable generated a response from Dan Connolly
[7] proposing that "But perhaps a little NOTE on how to support local
copies of stuff in the Web, especially in XML software, would be useful" -
a possible step forward, but a very small one.

It seems like the W3C is pushing hard to use URIs to identify everything
possible, without giving much concern to the difficult questions that have
bedeviled the xml-uri list for the past two months.  While the URI
community seems happy to have identifiers that are processed using a wide
variety of different rules, I'm not sure that approach is acceptable for
XML processing.  (It could become acceptable were URI processing and
comparison, at least in an XML context, defined more clearly and explicitly.)

While I welcome the effort to reuse existing parts, and could be persuaded
that URIs are a good answer to all of these problems, I don't think that
URIs are anywhere near mature or specified enough to carry the burdens that
various XML specifications are placing on them.  There is no reason to
expect URI processing to be as predictable as XML processing (even with the
many possibilities in XML processing), and I'm very worried that URIs are a
threat to XML processing in the absence of constraints that would make URI
processing and usage predictable.


[1] - http://lists.w3.org/Archives/Public/xml-uri/2000Jul/0005.html
[2] - http://lists.w3.org/Archives/Public/xml-uri/2000Jul/0009.html
      http://lists.w3.org/Archives/Public/xml-uri/2000Jul/0011.html
[3] - http://www.w3.org/TR/xlink/#link-semantics
[4] -
http://lists.w3.org/Archives/Public/www-xml-linking-comments/2000JulSep/0013
.html
[5] - http://lists.w3.org/Archives/Public/xml-uri/2000Jul/0016.html
[6] - http://lists.w3.org/Archives/Public/xmlschema-dev/2000Jul/
[7] - http://lists.w3.org/Archives/Public/xmlschema-dev/2000Jul/0006.html

Simon St.Laurent
XML Elements of Style / XML: A Primer, 2nd Ed.
http://www.simonstl.com - XML essays and books

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