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RE: A note on the challenge presented by open content models

From: Martin Gudgin <mgudgin@microsoft.com>
Date: Thu, 17 Oct 2002 10:52:31 -0700
Message-ID: <92456F6B84D1324C943905BEEAE0278E02D3092F@RED-MSG-10.redmond.corp.microsoft.com>
To: "Amelia A Lewis" <alewis@tibco.com>, "WS-Desc WG (Public)" <www-ws-desc@w3.org>

With the WSDL schema we could define an abstract globel element decl for
each location and tell people to put their extensibility element in the
substitution group for the element that corresponds to the location they
want to 'extend' in. I need to think about how that would work for
extensibility elements that need to appear in multiple places ( not sure
if we have a use case for that )

Gudge



> -----Original Message-----
> From: Amelia A Lewis [mailto:alewis@tibco.com] 
> Sent: 17 October 2002 10:34
> To: WS-Desc WG (Public)
> Subject: A note on the challenge presented by open content models
> 
> 
> 
> As a result of discussions during today's teleconference, and 
> related work for support of features and the like, it occurs 
> to me that existing schema models and languages are not 
> terribly well-adapted to open content models.  I thought that 
> I would share these thoughts (lucky you!).
> 
> At issue is the fact that there is, at least conceptually, a 
> schema for WSDL.  It has an open content model, which can be 
> represented in W3C XML Schema as any, namespace ##other.  
> This is true for almost all elements in WSDL.
> 
> Particular extensions, as a rule, define a sort of 
> micro-vocabulary intended for use within the context of given 
> extensibility elements in WSDL.  That is, the elements and 
> attributes defined for a DIME binding (for instance) would 
> have particular constraints.  Some should appear as children 
> of wsdl:binding, others as children of wsdl:operation, others 
> as children of wsdl:input, wsdl:output, or wsdl:fault.  There 
> might also be elements or attributes intended to decorate 
> wsdl:service or wsdl:port.
> 
> But there is no way, so far as I know, in any schema 
> language, to express the required *parent* of an 
> extensibility element.  It's an interesting omission, once 
> one considers it.  A deliberately open content model, in 
> which the extension specifications constrain themselves (in 
> effect) is not contemplated, and not supported (admittedly, 
> formalizing such a thing carries some interesting security issues).
> 
> This is not an issue for resolution, just for its 
> thought-provoking qualities.  It appears that the path being 
> traveled by WSDL (an open content model for the base schema, 
> with extensions expected to specify their preferred or 
> required inclusion locations) is not well known.  It may 
> present obstacles in terms of defining schemas for such extensions.
> 
> Amy!
> -- 
> Amelia A. Lewis
> Architect, TIBCO/Extensibility, Inc.
> alewis@tibco.com
> 
> 
Received on Thursday, 17 October 2002 13:53:29 GMT

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