RE: Examples of substitution group extending WSDL.

Jacek proposed adding some RDF-specific wrappers into WSDL 1.2.  Having
assumed our extensibility model was sufficient for this, I set out to
prove it and instead found it difficult to combine an existing schema
with the WSDL schema in order to use it as an extension.  We're trying
to balance the expressive power of the schema (better with substitution
groups) with ease of composition (open content model) with additional
support for certain other namespaces (built-in wrappers).

> -----Original Message-----
> From: David Orchard [mailto:dorchard@bea.com]
> Sent: Friday, June 27, 2003 1:41 PM
> To: Jonathan Marsh; www-ws-desc@w3.org
> Subject: RE: Examples of substitution group extending WSDL.
> 
> 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 Tuesday, 1 July 2003 18:03:26 UTC