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RE: Examples of substitution group extending WSDL.

From: David Orchard <dorchard@bea.com>
Date: Fri, 27 Jun 2003 13:40:53 -0700
To: "'Jonathan Marsh'" <jmarsh@microsoft.com>, <www-ws-desc@w3.org>
Message-ID: <024c01c33cec$67eb5410$7106a8c0@beasys.com>
Jonathan,

I was curious as to the motivation for this.  Is this simply to see how 3rd
party extensions get added to wsdl 1.2 and how to make them required in
messages?  Or is this looking at backwards/forwards compatibility wrt wsdl
1.2?

I tend to agree with Jack that redefining 3rd party extensions to insert
wsdl:required is bad.

Dave

> -----Original Message-----
> From: www-ws-desc-request@w3.org [mailto:www-ws-desc-request@w3.org]On
> Behalf Of Jonathan Marsh
> Sent: Wednesday, June 18, 2003 7:48 AM
> To: www-ws-desc@w3.org
> Subject: Examples of substitution group extending WSDL.
> 
> 
> 
> Results of my tinkering below.
> 
> First, I created an instance with a brand new extension to see how a
> fresh extension schema would work.
>  
>   <definitions xmlns="http://www.w3.org/@@@@/@@/wsdl"
>                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>                xmlns:my="http://www.example.com/extensions/mine"
>  
> xsi:schemaLocation="http://www.example.com/extensions/mine 
> extension.xsd
> http://www.w3.org/@@@@/@@/wsdl wsdl.xsd"
>                targetNamespace="http://example.com/jonathan/test">
>     <documentation>This file tests validation of an extended WSDL
> document</documentation>
>     <my:extension>Jonathan Marsh</my:extension>
>   </definitions>
> 
> I described this extension with a schema, and inserted it into the
> globalExt substitution group (which allows the extension to appear at
> the top level, and almost anywhere else, within WSDL).
> 
>   <xs:schema targetNamespace="http://www.example.com/extensions/mine"
>              xmlns:wsdl="http://www.w3.org/@@@@/@@/wsdl"
>              xmlns:xs="http://www.w3.org/2001/XMLSchema"
>              elementFormDefault="qualified">
>     <xs:import namespace="http://www.w3.org/@@@@/@@/wsdl"
>                schemaLocation="wsdl.xsd"/>
>     <xs:element name="extension" type="xs:string"
>                 substitutionGroup="wsdl:globalExt"/>
>   </xs:schema>
> 
> Notes:
> 1) The extension schema imports the wsdl schema for the purpose of 
>    allowing the substitution group to be specified.
> 2) The validator needs to associate both the extension schema and 
>    the WSDL schema.  In this case I used the xsi:schemaLocation 
>    mechanism.
> 
> 
> Next I took an existing vocabulary (DSig) and tried to embed it in the
> WSDL.
> 
>   <definitions xmlns="http://www.w3.org/@@@@/@@/wsdl"
>                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>                xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
>                xsi:schemaLocation="http://www.w3.org/2000/09/xmldsig#
> wsdl+dsig.xsd http://www.w3.org/@@@@/@@/wsdl wsdl.xsd"
>                targetNamespace="http://example.com/jonathan/test">
>     <documentation>This file tests validation of an extended WSDL
> document</documentation>
>     <ds:Signature>
>       <ds:SignedInfo>
>         <ds:CanonicalizationMethod
> Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
>         <ds:SignatureMethod
> Algorithm="http://www.w3.org/2000/09/xmldsig#dsa-sha1"/>
>         <ds:Reference
> URI="http://www.w3.org/TR/2000/REC-xhtml1-20000126/">
>           <ds:Transforms>
>             <ds:Transform
> Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
>           </ds:Transforms>
>           <ds:DigestMethod
> Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"/>
>           
> <ds:DigestValue>j6lwx3rvEPO0vKtMup4NbeVu8nk=</ds:DigestValue>
>         </ds:Reference>
>       </ds:SignedInfo>
>       <ds:SignatureValue>MC0CFFrVLtRlk=...</ds:SignatureValue>
>     </ds:Signature>
>   </definitions>
> 
> In order to validate this, I had to modify the DSig schema
> (wsdl+dsig.xsd) in three ways:
> 1) Add an appropriate substitutionGroup attribute, with the value of a
> WSDL extension group QName.
> 2) Declare WSDL namespace prefix so the QName is valid.
> 3) Add an import of the wsdl schema so the QName reference is 
> complete.
> 
> (new lines marked with "|")
> 
>   <schema targetNamespace="http://www.w3.org/2000/09/xmldsig#"
>           ...>
> |   <import namespace="http://www.w3.org/@@@@/@@/wsdl"
> |           schemaLocation="wsdl.xsd"/>
>     <element name="Signature" type="ds:SignatureType"
> |            substitutionGroup="wsdl:globalExt"
> |            xmlns:wsdl="http://www.w3.org/@@@@/@@/wsdl"/>
>     ...
>   </schema> 
> 
> Then I attempted the holy grail, a simple wrapper schema that 
> would have
> the effect of the schema above, while importing the DSig 
> schema without
> modification.  I failed in this because:
> - Element declarations in an imported schema cannot be overridden.
> - Redefine does not work on element declarations.
> - There is no other way to add elements to a substitution group.
> 
> I rejected modifications to the instance document that would enable a
> wrapper schema:
> - Changing the namespace of the top level element.
> - Introducing a wrapper element.
> 
> My conclusion is that the cleanest way to enable this scenario was
> copying and modifying the DSig schema with the simple additions found
> above.  I also note that this would be necessary to allow 
> wsdl:required
> attributes to appear on ds:Signature elements.
> 
> Do we find this limitation acceptable?  Does this limitation outweigh
> the benefits of our substitution group extensibility mechanism?
> 
> 
> 


Received on Friday, 27 June 2003 16:41:16 GMT

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