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   Re: [xml-dev] dynamically generated XML Schema?! R: [xml-dev] Number of

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  • To: xml-dev@lists.xml.org
  • Subject: Re: [xml-dev] dynamically generated XML Schema?! R: [xml-dev] Number of active public XML schemas
  • From: Chizzolini Stefano <chist@csb.it>
  • Date: Wed, 3 Nov 2004 15:27:30 +0100

> -----Messaggio originale-----
> Da:	Burak Emir [SMTP:Burak.Emir@epfl.ch]
> Inviato:	mercoledý 3 novembre 2004 11.25
> A:	Chizzolini Stefano
> Cc:	xml-dev@lists.xml.org
> Oggetto:	dynamically generated XML Schema?! Re: [xml-dev] R:
> [xml-dev] Number of active public XML schemas
> Chizzolini Stefano wrote:
> >>Which raises an interesting question: Should there be a non-XML syntax 
> >>for XSDs like there is for RELAX NG? It's always been an article of
> >>faith for me that schemas should be written in XML, if for no other
> >>reason than not having to write another parser. But one does have to
> wonder...
>>I think there are some valid reasons for writing schemas in XML:
>>seamlessness, elegance and power. Adopting a "self-describing" language
>>syntax avoids the users from learning a new one and allows to leverage
>>existing applications derived from the original spec (in this case, XML
>>spec); I mean, for example, the chance to dynamically generate brand new
>>schemas through XSL transformations.
>One can of course endlessly discuss about syntax, but I have never 
>understood the obsessiveness of marking up descriptions of XML data in XML.
>Who needs to dynamically generate schemas? The whole point of schemas is 
>to be a widespread, well understood description of instances.
>If you generate a shining brandnew schema dynamically using X, you end 
>up with a description that did not exist before. Ergo, the risk is that 
>you do not have conforming documents.

You are reasoning on a static-scenario base! Instead, I imagine (for
example) the downstream work an agent could do depending on *that*
dynamically-generated schema: it could create dynamic database schemas or
even dynamically-conforming documents (but that's likely to be more suitable
for a semantically-rich scenario as the semantic web).
Anyway, I'm fascinated by the theoretical approach about language
generation: I wouldn't throw away *just* the mathematical possibility to
escalate an initial vocabulary through a pattern. Don't you care about it?

>Now one can dwell in discussion of hypothetical families of schemas, but 
>for all my experience tells me about modelling, if you manage to 
>understand what the common things are that make a bunch of schemas a 
>family, then you can anticipate the extensibility you need, which 
>removes completely the need for dynamic generation.
>What is a use case for dynamically generated schemas?
>Why does one need to use XSL for it ?

(See above)

>Why couldn't one use non-XML syntax for it?

Simply because of its lack of transformability.



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