[dsdl-discuss] Re: Reformulation of MNS for DSDL Part 4

On Fri, 11 Apr 2003 16:29:30 +1000
"Rick Jelliffe" <ricko@topologi.com> wrote:

> From: "MURATA Makoto" <murata@hokkaido.email.ne.jp>
>
> > First, I am not sure if Draconian validation (i.e., if invalid then halt)
> > is really needed. Neither RELAX NG nor DTDs provide such mechanisms.
>
> DTDs certainly halt when a content model validity error is found, in most (all?) implementations I have seen. In fact, one of the talking points on Schematron
> when it came out was that it didn't just stop on the first error.

I do not see what you mean. In the case of Xerces-J, validation
error recovery is controlled by application programs. In other words,
it is up to your implementation of the function error(SAXParseException ex).
If this function do not stop the parser, validation certainly continues.
I think that this is fine and do not see any reasons to introduce any
mechanisms at the schema language level.

In the case of RELAX NG, there is an API called JARV. It certainly
allows user-defined error handlers.

http://iso-relax.sourceforge.net/apiDoc/org/iso_relax/verifier/Verifier.html#setErrorHandler(org.xml.sax.ErrorHandler)

> To give an example, my company is just about to release a proxy validator: ...

Your example makes sense. But I still do not see any reasons to
introduce any Draconian-validation-error handling mechanisms at
the schema language level. You can certainly do anything in your validation
error handler.

>
> I guess the nub of the problem is how to make modular schema
> languages work together effectively: to prevent unnecessary processing,
> detect errors early, and not generate duplicate or redundant error messages.
>
> If "halt" seems to procedural, then perhaps an attribute like
> severity="fatal" might be more acceptable? So if the DSDL implementations
> supports (and is invoked with) "halt-on-severe-error" and a schema
> has a fatal error, the rest of the validations in that part 4 module terminate.

Even when we use a collection of schemas against a single document,
I still think that error handlers can implement the "if-invavild-then-halt"
strategy and that no mechanisms are needed at the schema language level.

> > Right. Moreover, you certainly disallow the mixture of two DOCBOOK
> > namespaces in a document.
>
> I don't think so. That is an extra validation requirement that can be
> handled by Schematron, for example. If someone cuts and pastes a fragment
> from OASIS DOCBOOK into a George Bush DOCBOOK document,
> and the editor is smart enough to move the namespace but not smart
> enough to correct it, the user should not have to suffer.

I meant that you might want to disallow such mixture and that
you certainly can if you want.

Cheers,

-- 
MURATA Makoto <murata@hokkaido.email.ne.jp>
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