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Re: XML language subset

From: Dan Connolly <connolly@w3.org>
Date: Fri, 31 Jan 2003 11:30:22 -0600
To: Christopher Welty <welty@us.ibm.com>
Cc: www-webont-wg@w3.org
Message-id: <1044034221.32644.379.camel@dirk.dm93.org>

On Fri, 2003-01-31 at 10:41, Christopher Welty wrote:
> I recently saw word that the W3C TAG is considering an "XML Subset" to 
> address concerns that XML is too complicated for a lot of implementors, 
> and some communities only needing a simpler subset would like it to be 
> standardized to facilitate interoperation.
> 
> I know I've heard a lot of grumbling and snide remarks about the three OWL 
> languages, and the fact that XML is considering going in the same 
> direction will help us make the case.

Maybe, maybe not...

[[[
Profiling XML, providing more implementation options, will
necessarily increase the possibility of interoperability problems
and it would be best to avoid doing so. Profiles are a bad idea
on general principles and are in direct conflict with one of the
original goals of XML[1]: "the number of optional features in XML
is to be kept to the absolute minimum, ideally zero."

Unfortunately, a number of user communities have expressed a need
to work with only a subset of XML. ...
]]]
-- [xmlProfiles-29] TAG recommendation for work on subset of XML 1.1
http://lists.w3.org/Archives/Public/www-tag/2003Jan/0418.html


Hardly a glowing endorsement of profiles/dialects/options.

Nothing the TAG has said argues in favor of optional levels
for their own sake. On the contrary; the tag has made
it pretty clear that they're generally a bad idea, and
that they have to be cost-justified on a case-by-case basis.

I gather our justification is in the overview, in section
  1.2 The three sublanguages of OWL
  http://www.ksl.stanford.edu/people/dlm/webont/OWLOverview.htm#s1.2

Hmm... it doesn't currently look right to me.

| OWL DL supports those users who want the maximum expressiveness
| while their reasoning systems maintain computational completeness
| (all conclusions are guaranteed to be computed) and decidability
| (all computations will finish in finite time).

>From recent discussions, it's not at all clear that this is the
expectation we should set around OWL DL. It's actually OWL Lite
that folks are saying they can do practically, right? oneOf
takes OWL DL into a complexity class that has no known practical
implementations, right?

And in drafting a Request for Proposed Recommendation status,
I'm starting to wonder where implementation experience
corresponding to a "complete OWL DL consistency checker"
is going to come from. I'll find it hard to put my name
on a request that doesn't have at least one real implementation
in that conformance class.

I think we have some work still to do to justify the three dialects.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Friday, 31 January 2003 12:31:19 GMT

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