[dsdl-discuss] Re: Selection criteira

On Tue, 2004-04-06 at 11:32, Alex Brown wrote:
> I think we've got a problem here in that, as originally set out, DSDL has
> Part 4 for 'selection of validation candidates'. Whenever (so I thought) we
> needed to select something then part 4 would provide comprehensive
> mechanisms for that purpose. I imagined this would be a fairly catholic
> language, perhaps allowing specification of existing and future query
> langauges (XPath, XQuery, etc.) to do the selection.
>
> Now NRL is lined-up to be 'part 4', and NRL is not a general purpose
> selection language but addresses the narrower problem of selection (and
> dispatch) of candidates per Namespace. So what has happened to the original
> idea of having a part specifically 'for' selection in all its forms?

Yes, that's a good point that has been discussed in Philadelphia.

> It seems to me now the burden of doing this is being shifted to Part 10.
> Whereas before (so I thought) Part 10 would be a coordinating language that
> *used* the language of part 4 to select and dispatch stuff to other parts of
> DSDL, we now have a model whereby Part 4 will select and dispatch candidates
> per Namespace, Part 10 will select and dispatch candidates for
> non-Namspace-based selections.

Part 10 allows to plug any transformation language and the idea is that
people can use let say XSLT 1.0, XSLT 2.0, STX or whatever if they want
to dispatch pieces of documents to different schemas in ways that part 4
do not cover.

> It seems a shame to me that while *parts* of the design of DSDL are based on
> gold-standard design principles (RELAX NG ...) the *overall* design is in
> danger of ending up in a state which will be likely to strike observers as
> an accidental mess.
>
> It would be fine is we were happy to throw everything together and then
> refactor like crazy, but we're instead pressing individual parts forward to
> standardisation without a clear picture of the whole in mind. IMHO this is
> asking for trouble.
>
> I think it is debatable whether DSDL needs or benefits from having a purely
> Namespace-based selection language as one of its parts. I don't think there
> is any benefit in having (different?) dispatching mechanisms in different
> parts of the standard.

At the moment, I don't think we have. At least, I can insure that there
is no dispatching mechanism in part 10 at the moment.

> I would like to consider as options:
>
> - Merging parts 4 & 10 to create a select/dispatch language for *all* type
> of selected candidates (aka DSDL framework)
>
> - (variations of above) expanding part 4 to encompass non Namespace-based
> selection and losing Part 10; or expanding part 10 to encompass
> Namespace-based selection and losing Part 4.
>
> - Rolling part 4 back to be more like the original 'selection of validation
> candidates' concept (as outlined above) - i.e., expanding its selection
> language to encompass non-Namespace-based selection tasks and removing its
> dispatching language. Then Part 10 would 'use' Part 4 for selection
> purposes.

Part 10 is currently both more and less than a selection language.

Its purpose is to provide a language that defines what it means for a
document to be "valid" or "invalid" in a declarative fashion by
combining the use of existing transformations and validations tools.

It has no selection mechanism built-in but can use transformations as
external selection mechanism and can also invoke a part 4 schema as a
validation.

Combinations are possible, such as using a XSLT transformation before
part 4 to split candidates from a monolithic vocabulary into different
namespaces so that they can be processed with part 4 (or eventually to
use part 8 to do so if part 8 supports transformations on namespaces).

Part 10 is like a "make" or "ant" system designed for validation
purposes only.

It can be seen as the glue needed to keep each of the parts based on
gold-standard design principles...

Eric

-- 
See you in Amsterdam.
                                               http://www.xmleurope.com/
Upcoming XML schema languages tutorial:
 - Amsterdam   -half day- (18/04/2004)        http://masl.to/?P220516D7
------------------------------------------------------------------------
Eric van der Vlist       http://xmlfr.org            http://dyomedea.com
(ISO) RELAX NG   ISBN:0-596-00421-4 http://oreilly.com/catalog/relax
(W3C) XML Schema ISBN:0-596-00252-1 http://oreilly.com/catalog/xmlschema
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