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RE: Are we losing out because of grammars?

> -----Original Message-----
> From: Eric van der Vlist [mailto:vdv@dyomedea.com]
> Sent: 02 February 2001 11:18
> Cc: xml-dev@lists.xml.org
> Subject: Re: Are we losing out because of grammars?
> Rick Jelliffe wrote:
> >
> > From: James Clark <jjc@jclark.com>
> >
> > >What is the point of this crusade against grammars?
> >
> > Oh, it is no crusade against grammars.
> To make it short, isn't the main difference that with Schematron
> everything that is not forbidden is allowed while with the other
> languages, everything that is not allowed is forbidden.

Of course Schematron also offers a great deal of other features which
don't seem to be high priorities in other languages.

While James' comments about efficiencies are well taken, I'd suggest
that while Schematron schemas may be more verbose, they are certainly
a lot more 'user-friendly'.

The ability to associated precise, readable feedback with fine-grained
constraints is a huge bonus from a user perspective. Yes, more work for
the maintainer, but less effort for the user.

I've recently had to pick up a particular chema for a first time, and
have ended up tracking through all sorts of documentation and DTDs
to track down reasons for some validation errors. Even RXP (may favourite
validation sanity checker) didn't produce much in the way of useful
feedback. Sure, I could find the offending element, and I knew it was
wrong, but I didn't know *why*.

A Schematron schema would have been a lot more useful.

I like Ricks 'map' and 'route' analogy. While a list of directions are
for guiding one from A to B, if you take a wrong turn then you're left
to go back to A and start again. If I had a map then you could just
said "here's A and there's B, get on with it" and I'd be able to
navigate my way. (maybe I'm pushing the analogy a bit far, but
I think the distinction has value).

Personally I think there's room for both approaches, and I don't think
we've even begun to discover all the possible uses of rule-based approaches.