[sc34wg3] Almost arbitrary markup in resourceData

Murray Altheim sc34wg3@isotopicmaps.org
Mon, 10 Nov 2003 23:08:22 +0000

Kal Ahmed wrote:
 > My feeling is that resourceData should allow only elements from
 > namespaces other than the XTM namespace(s).

Well, you guys both probably know my feeling on this one. I'd prefer to
simply keep all other markup out of XTM. We as a group made a decision
on this design principle, and I for one will simply not modify my tools
to handle the muck of markup that will result if you begin letting people
stick SVG, XHTML and anything else in <resourceData>. I've never found
the argument pro this weighs against the argument con, which is that
XTM is an interchange format, and you *completely* lose the interchange
of an XTM document if you no longer know whether all processors are
going to know what to do with "wild" markup. You have a loss of meaning
and a loss of predictability.

 > On Mon, 2003-11-10 at 19:07, Lars Marius Garshol wrote:
 >>I'm working on extending the RELAX-NG schema for XTM 1.1 to support
 >>arbitrary markup in <resourceData> and <baseNameString/> and ran into
 >>some questions.
 >>The first is: do we want to allow XTM elements to appear inside these
 >>elements? That is, is
 >>  <resourceData>XTM is an <topicRef xlink:href="#XML"/>-based markup
 >>  language.</resourceData>
 >>OK? If so, what does it mean? Is it OK for <scope> to appear here? For
 >><topicMap/>? For <resourceData>?
 >>And what about this
 >>  <resourceData>XTM is <em>really</em> cool.</resourceData>
 >>is that OK? (This is a trick question: the XTM namespace is the
 >>default namespace, so 'em' will be posing as an XTM element here,
 >>since it will be in the XTM namespace.)
 >>This is clearly OK, however:
 >>  <resourceData>XTM is <xhtml:em>really</xhtml:em>
 >>  cool.</resourceData>

In my opinion, it's clear not okay, and not cool. The first time somebody
opens up that topic map and sees *nothing* it's not cool. And which
version(s) of XHTML are you going to allow? There's about five right now.
There will be more, many more. Or can people put *anything* there?

 >>I can easily write the RELAX-NG rules for this, whatever we decide,
 >>but I think we need to consider this carefully so that we don't trip
 >>ourselves (and others) up.

I don't buy for a minute the typical W3C argument that you can just
ignore markup you don't understand. That's a proprietary hole in
XTM, where vendors will be able to "legally" put proprietary markup
that other users will have to play catch-up to correctly process.

I think the whole thing smells. That's been my opinion of mixed namespace
markup since about 1998, so I suppose there's no surprise. The only way
I'd want to approach this would be to create *specific* XTM DTDs that mixed
specific markup languages, like XTM 1.0 plus a specific subset of XHTML
Strict, say, a subset of block and inline markup (but no <applet>, <object>,
<script>, etc.). And then you can just refuse the documents you don't know
what to do with. But this in the full knowledge that suddenly there's more
than one XML interchange markup language for topic maps, which simply
can't be a good thing for our community, our vendors, our potential


Murray Altheim                         http://kmi.open.ac.uk/people/murray/
Knowledge Media Institute
The Open University, Milton Keynes, Bucks, MK7 6AA, UK                    .

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