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RE: xslt stylesheet for xforms to xhtml

From: Mark Seaborne <MSeaborne@origoservices.com>
Date: Mon, 2 Sep 2002 10:28:50 +0100
Message-ID: <DC65AE678B89004B9CCB202E19482CC704FAD2@mail.origoservices.local>
To: <www-forms@w3.org>

-----Original Message-----
From: Robert Trybis [mailto:rt@cygnets.co.uk]
Sent: 30 August 2002 18:03
To: www-forms@w3.org
Subject: RE: xslt stylesheet for xforms to xhtml

>I don't think I am really missing the point though, especially not if
>it's the most asked question on the list.
>I know xforms is much more than UI markup, but all I want to do is UI
>markup - and I would like to do it now. 
>That is probably what the other people who asked the same question are
>also trying to do.

That is interesting. The thing that attracts me to XForms is not really the UI bit, but the model. I think this is where the key prospect for reusability lies. I work for a message standards body, and we currently maintain our own XForms like language, that companies in the industry use to build forms based applications. It makes a half-hearted attempt to separate the UI from the model, but fails. So our forms have to be authored entirely with a specific renderer in mind. My hope for XForms is that the model should become fully portable across implementations.

My main niggle with XForms is that the binding/validation functionality seems to be there largely to compensate for lack of same in W3C XML Schema; which makes that bit of XForms into a schema language. We have ourselves recognised problems with the expressiveness of W3C XML Schema, and at the moment all the schemas we publish are supplemented by message implementation guidelines; prose documents which tell you about all the data dependencies and validation rules about which W3C XML Schema remain silent. Rather than inventing our own vocabulary to add to what W3C XML Schema already does, we are instead investigating the use of existing schema languages to achieve this. The most obvious candidates to fulfil this function are Relax NG and Schematron, especially as these have, or are about to receive official status from ISO. I do not know for certain, but I strongly suspect that the majority of what is currently prose will in the future be expressed in one or other of these schema languages.

The data dependencies and validation rules that an XForms application must be capable of enforcing are, at least for the industry in which I work, exactly those which an application generating XML instances without human intervention must enforce (if I am over-simplifying, I would be really grateful if someone would put me straight on this). The differences arise only at the implementation level, it seems. So my hope is that one bundle of schemas will form the basis of any application required to process/generate our messages. 

Which begs the question: should XForms be adding yet another language for expressing schema-like constraints on XML documents? Given that XForms is required to function without external schemas at all, then the obvious answer is yes. Naturally, I would be very happy if XForms, in addition to what it already does, provided me with a method for linking instances to a) more than one schema; b) expressed in more than one schema language. However, I am reconciled to the fact that, at some point in the not too distant future, I will be looking to provide mappings between the bits that XForms adds to validation and any equivalent functionality provided by non-W3C schema languages.

All the best

Mark Seaborne

Origo Services Ltd
Received on Monday, 2 September 2002 05:29:13 UTC

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