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New Issue: Support of evolution of messages described in Schema 1.0

From: <paul.downey@bt.com>
Date: Fri, 15 Apr 2005 00:07:24 +0100
Message-ID: <2B7789AAED12954AAD214AEAC13ACCEF2709E207@i2km02-ukbr.domain1.systemhost.net>
To: <www-ws-desc@w3.org>

Following our decision to retire Jonathan's issue to get a joint task  
force with the XML Schema WG, I took an action item to propose a new  
issue for extensibility/versioning for wsdl using schema 1.0 [1]:

Issue: Support for evolution of messages described in Schema 1.0

The XML Schema Working Group is currently collecting use cases for  
versioning [2] and are likely to provide support for more 'open content' 
in Schema 1.1. This direction is supported by members of the WSD WG 
who would like WSDLs using Schema 1.0 to be able to describe message 
contents which may compatibly evolve within a given namespace.

Describing messages with more open content in Schema 1.0, whilst  
possible, is an unnatural and difficult enough activity to be the subject 
of numerous articles and conference papers, some written by members 
of this WG, offering techniques for publishers to provide extensibility  
points in schemas. An author has to know in advance where content
will be added in the future; it's not possible to evolve schemas 
published by a third party, unless they have provided such extensibility

Abstract Proposal:
WSDL could define how a type description relates to a message, either  
specifically for schema 1.0 or through a "schemaProcessingStyle"

That is a WSDL could describe how a schema processor should be employed  
when building or parsing messages. An example of such a processing 
style is a technique demonstrated by Henry Thompson [3] whereby the 
PSVI from a first pass validation of a message is processed to remove 
unexpected content from a message before validating the message again, 
thereby enabling more open message content.



[2] http://www.w3.org/XML/2005/xsd-versioning-use-cases/

[3] Henry Thompson, XML2004 "Versioning made easy with W3C Schema":
Received on Thursday, 14 April 2005 23:07:29 UTC

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