Hi,
At 08:49 PM 1/31/2010, Stuart wrote:
>Birnbaum, David J wrote:
>>Dear TEI-L,
>>
>>>There is a useful commentary on this in David J. Birnbaum, "In
>>>Defense of Invalid SGML", ACH/ALLC
>>>1997, Queen's University, Kingston, ON.
>>>http://xml.coverpages.org/birnbaumACH97.html
>>An updated version of that report is available on-line at:
>>
>>http://clover.slavic.pitt.edu/~djb/sgml/invalid.html
>
>At the NZETC, we solve this by resorting to schematron, which issues
>warnings rather than errors. A significant minority of our texts
>have schematron errors because the schematron reflects how we'd like
>the world to work, rather than how it does.
>
>Yes, I understand that this is just moving the problem from DTD to
>schematron, but almost all modern XML tools provide little or not
>XML support once you venture off the DTD-beaten track.
In my experience, "just moving the problem from DTD to Schematron" is
more significant and more helpful than it might appear at first.
This is because many (most) systems assume their DTDs will be
gatekeepers -- "invalid documents shall not pass" -- which is
entirely inappropriate to the kind of interesting and important
irregularity that David wrote about.
This also goes to the heart of the requirements clash between
prospective markup, i.e. XML encoding done for the sake of fitting
data to a particular application or family of applications -- which
typically require at least some forms of regularity and
predictability -- and retrospective markup, which aims to *describe*
documents irrespective of concerns with how regular they are, and
which may be as interested in irregularities as in regularities. It's
not that prospective and retrospective aims cannot be reconciled:
they can. But to do so requires a fair amount of art.
To that end, placing "hard" validation requirements in a
grammar-based schema such as a DTD or RNG schema -- but modelling
loosely -- while relegating "soft", heuristic validation (which can
potentially be much tighter, since to fail a test is not considered
ipso facto an error) to a rules-based approach such as a Schematron
or XSLT-based tag checker, is a very workable approach.
I wrote about all this back in my paper of 2001, "Beyond the
'Descriptive vs Procedural' Distinction" --
http://piez.org/wendell/papers/beyonddistinction.pdf
Cheers,
Wendell
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