[dsdl-discuss] Re: Namespace processing

From: "MURATA Makoto" <murata@hokkaido.email.ne.jp>

> MNS requires significant extensions to my implementation strategy. In particular
> modes do require extensions (probably we need a stack of modes). However, I
> do no think that MNS requires monolithic implementations.

What does James think?
 
> > But almost none of MNS is applicable to Schematron, so I think it
> > is a worthwhile question to ask if there is some other way to reformulate
> > it (in particular, using XPaths) which may make it more general.
>
> Now, I understand your concern. It would be helpful if you show why MNS
> or the Part 4 CD cannot play with Schematron. I think that no mechanisms
> in MNS or Part4 CD are closely related with RELAX NG and that they can
> play with Schematron very well. I may be mistaken, since my understanding
> of Schematron is limited. But I would like to see clear reasons that
> MNS does not play with Schematron.

It is not that it cannot play, it is just that it is probably irrelevant, because it
does not offer much expressive power that I can see. So I suspect Part 4
should be more RELAX-specific, or specify configurations to be sent to validators
to select the view they use, or provide the kinds of things in Namespace
Switchboard more.

Schematron uses the context mechanism to select which elements to
validate. So a prior mechanism of candidate selection is not strictly
needed. Schematron allows paths in contexts, so the mode mechansim
is not strictly needed. Schematron has never made any assumption
of 1 schema per namespace (in fact, I have always found this assumption
to be perverse), so an extra mechanism to select schemas based on
namespaces is not strictly needed either.

So, from that POV, the need for being able to select candidates
to validate is to promote efficiency and to be able to abort
before expensive further validation passes are attempted.

Furthermore, assuming that Schematron schemas are used as the "second line
of defense" after RELAX NG, I have a feeling that the kinds of constraints
that Schematron schemas would be used for would tend to be
those that are left over *after* Part 2+Part 4 validation occurs.

I expect Schematron would be used for constraints which require
random access and document scope, such as looking for //*[@id];
divide-and-conquer is obviously not appropriate for that.

Cheers
Rick Jelliffe

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