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Thanks, James. A comment, though ...
On Thu, 03 Jul 2003 09:43:02 +0700
James Clark <jjc@jclark.com> wrote:
> As regards list, RELAX NG is already providing more than W3C XML
> Schema. For example, in RELAX NG you can have a list of an NCName
> followed by a URI. As for why we didn't go further than this and
> support non-whitespace separated lists, I think there was doubt as to
> whether this was pushing the envelope in the right direction. Isn't
> it better to mark up complex structure explicitly with elements and
> attributes? The general policy for version 1.0 was only to put in
> features that we were sure about it. Non-whitespace separated lists
> are something that could easily be added in version 2 if experience
> with version 1.0 shows it to be desirable.
The ability to define textual data types with complex patterns (rather
than breaking the pattern apart into markup) appears to be one of the
most common requests from folks who are willing to question the
orthodoxy of W3C XML Schema. A number of such requirements have been
mentioned on this list (geographic location information (lat/long),
complex numbers, rational numbers (fractions), and alternative date
formats come immediately to mind).
Lists are another of these. At present, only white space separation is
allowed; the extension to permit other separators is straightforward.
While one could argue that all such lists could be represented by
sequences of elements, it is equally true for whitespace separated
lists. In SGML, the list types were restricted to attributes, and were
expected to have pointer/reference semantics (ids, names); the
restriction made sense. Once it is possible to use list types to
constrain the content of elements, it is less clear that restricting the
list types to hold only tokens is justifiable.
On the other hand, this might be properly the job of the ISO type
description language, or of some other body willing to take on the task,
rather than RELAX NG.
Amy!
--
Amelia A. Lewis amyzing {at} talsever.com
"...Tests are a gift. And great tests are a great gift. To fail the
test is a misfortune. But to refuse the test is to refuse the gift,
and something worse, more irrevocable, than misfortune."
-- Cordelia Naismith Vorkosigan
[Lois McMasters Bujold, "Shards of Honor"]
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