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RE: Optional Extensions

From: David Orchard <dorchard@bea.com>
Date: Mon, 26 Jan 2004 12:47:55 -0800
To: "'Philippe Le Hegaret'" <plh@w3.org>, "'David Orchard'" <dorchard@bea.com>
Cc: "'Web Services Description'" <www-ws-desc@w3.org>
Message-ID: <02db01c3e44d$ad13da40$6401a8c0@beasys.com>

Philippe, you are not understanding the relationship between ignoring
content and extensibility/versioning.  If somebody makes a backwards
compatible change to their wsdl by putting in an optional extension, they
want to make sure that folks that don't know about their extension will not
fall over and die.  By underspecifying the behaviour of optional extensions
in wsdl, they do not have an assurance that their change is backwards
compatible.  By requiring that unknown extensions are ignored, there are
assurances of compatible evolution.  This model worked very well for HTML
and HTTP headers, and is embodied in the soap:mustUnderstand attribute.
There is extensive precedence for this.

Cheers,
Dave
> -----Original Message-----
> From: Philippe Le Hegaret [mailto:plh@w3.org]
> Sent: Monday, January 26, 2004 12:37 PM
> To: David Orchard
> Cc: Web Services Description
> Subject: Re: Optional Extensions
>
>
> On Mon, 2004-01-26 at 14:51, David Orchard wrote:
> > If there is a WSDL extension which is not mandatory and not
> recognized by
> > the WSDL processor what is to be done with it?  Our
> suggestion is that it
> > should be ignored, and that this should be specified.  Same
> thing applies to
> > extension attributes.
>
> Why should it be ignored? I would prefer a MAY rather a SHOULD. If you
> really want it to be ignored, don't put it in the place. If it's there
> and optional, it's up to the WSDL engine to use it.
>
> Also, one can define a required element (or a required feature) and
> include in the definition of it than all elements or attributes in a
> certain namespace MUST be processed (in fact, I recently worked on a
> WSDL extension using a feature to require the process of an
> attribute in
> a foreign attribute).
>
> Philippe
>
>
Received on Monday, 26 January 2004 15:52:24 GMT

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