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Issue 25: Interaction between W3C XML Schema and SOAP Data Model

From: Martin Gudgin <mgudgin@microsoft.com>
Date: Tue, 25 Jun 2002 19:18:47 -0700
Message-ID: <92456F6B84D1324C943905BEEAE0278E0145CCD7@RED-MSG-10.redmond.corp.microsoft.com>
To: <www-ws-desc@w3.org>

I took an AI at the last telcon to write up Issue 25. Here is that write
up.

The issue is regarding the relationship ( or lack thereof ) between XML
Schema and the SOAP Data Model.

WSDL 1.1 allows rpc/encoded endpoints to be described using XML Schema
type definitions. Unfortunately the 'encodedness' of the message means
that the schema type often does not actually describe the XML that is
placed on the wire. This is akin to saying 'You see that schema type
over there? Well the XML doesn't look like that!'

The problem stems from the fact the SOAP 1.1 data model ( not that there
is such a beast formally ) describes a directed edge labeled graph while
XML Schema descibes edge labelled trees.

In SOAP 1.2 we addressed this issue by seperating XML Schema out from
the SOAP Data Model and stating what would happen given certain
scenarios;

1.	Reading a message with no associated schema
2.	Reading a message and validating with <xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema' />
3.	Reading a message and validating with
http://www.w3.org/2000/12/soap-encoding.xsd
4.	Reading a message and validating against a message specific
schema

At the level of the SOAP data model all that happens is that the values
of the type properties of graph nodes get more precise as you move from
scenario 1 to 4.

I'm not sure what to propose for WSDL. Ideally we would clean up the
encoded stuff so that it could be described accurately using XML Schema
but I think that's probably a bigger job than we want to tackle right
now. Ditching encoding would do the trick but I don't know what other
people think about that.

Discussion?

Gudge
Received on Tuesday, 25 June 2002 22:19:18 GMT

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