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RE: Pluggability of Schema Languages in WSDL

From: Jonathan Marsh <jmarsh@microsoft.com>
Date: Sat, 28 May 2005 15:04:35 -0700
Message-ID: <7DA77BF2392448449D094BCEF67569A507B4A2FA@RED-MSG-30.redmond.corp.microsoft.com>
To: "Wes Moulder" <wes@webmethods.com>, "Edward Peters" <EPeters@webMethods.com>
Cc: <public-ws-desc-comments@w3.org>

Thank you for your comment - we tracked this as a Last Call comment LC70
[1].  The Working Group took several actions in response.

First, we agreed to remove the DTD and RelaxNG examples from the spec
and publish them as a Note (since they appeared more specificational
than informational.  @@This has not yet been reflected in the docs.@@

We also agreed to clarify in sec 2.1.3 and elsewhere that there is only
a single element declaration in the set for each QName.

During this discussion, we agreed that it is difficult to define the
behavior of extensions, but see the ability to describe message types in
alternate schema languages as useful (e.g. versioning).  As a result we
added the statement:

"This specification does not define the behavior of a WSDL 2.0 document
that uses multiple schema languages for describing type system
components simultaneously." 

You can view the resolution in context at [2].  If we don't hear
otherwise within two weeks, we will assume this satisfies your concern.

[1] http://www.w3.org/2002/ws/desc/4/lc-issues/issues.html#LC70
[2] http://www.w3.org/TR/2005/WD-wsdl20-20050510/#Description_details


> -----Original Message-----
> From: public-ws-desc-comments-request@w3.org [mailto:public-ws-desc-
> comments-request@w3.org] On Behalf Of Wes Moulder
> Sent: Wednesday, October 20, 2004 11:26 AM
> To: public-ws-desc-comments@w3.org
> Cc: Asir Vedamuthu
> Subject: Pluggability of Schema Languages in WSDL
> 
> 
> [note: This comment comes from both Asir Vedamuthu and Wes Moulder.
>        For further info, please talk to Asir.]
> 
> It feels like there is an unclear break between WSDL and XML Schema.
> It
> seems obvious that the idea was to allow multiple schema languages for
> XML to be used within the context of WSDL, however we find several
> concerns over this.
> 
> 1) The spec requires anything which understands WSDL to understand XML
> Schema.  This means that anything which could gain by being decoupled
> from XML Schema (IE platforms which do not have a schema processor)
> immediately takes that hit, because it has to support XML Schema. XML
> Schema has been reified into the Object Model for the Type System that
> WSDL uses, with loose words about how to deal with DTDs and Relax NG.
> 
> Reference - "Note: Support for the W3C XML Schema Description Language
>  is required of all processors."
> - http://www.w3.org/TR/2004/WD-wsdl20-20040803/#eii-types
> 
> 2) This feels a bit like inventing how these two xml schema languages
> are used in WSDL rather than standardizing what has been done (see
> http://www.w3.org/TR/2004/WD-wsdl20-20040803/#dtd).  Having actual
> implementations of a WSDL Generator and a WSDL Processor which
> actually
> use these and interoperate with each other should be a requirement
> before we include them in the final version of the spec.
> 
> 3) We are still unclear on what should happen if more than one schema
> language is used. What if they say different things?
> 
> 4) Overloading the use of the element AII for Message Reference
> Components, to refer components from different schema languages, seems
> like a "bad thing"(tm).  If a WSDL processor only understands XML
> Schema, and it goes to retreive the element AII from a Message
> Reference,
> and it is not a QName that refers to a Schema component, it will cause
> confusion and delay. (Yes, Wes's son is a Thomas fan.)
> 
> To counter all of this we have two alternate proposals and one
> requirement.
> 
> Proposal a) Break out XML Schema from the spec.  Introduce a schema
> language "binding" (terribly overloaded term at the moment).  Describe
> in the Types section (part 1 section 3) the part of this binding that
> belongs here.  Describe in the Message Reference Component section
> (part 1 section 2.5) the part of this binding that belongs here.
> Say nothing about XML Schema in the spec.  Introduce an AII on the
> types
> section which defines which schema language binding is in use, and
> state
> that a processor which does not understand the value of this AII must
> fault.  Have the wsdl processor fail if it does not understand the
> referenced schema language binding.  Introduce an adjunct to the spec
> defining the XML Schema schema language binding, making it optional.
> 
> Proposal b)  Drop RelaxNG and DTD from the spec and stay coupled to
> XML
> Schema.
> 
> Requirement) WSDL WG should demonstrate that such schema languages
> within
> WSDL are implementable and there are at least two different
> interoperable
> implementations of DTD and Relax NG type systems within WSDL.
> Having actual implementations of a WSDL Generator and a
> WSDL Processor which actually use these and interoperate with each
> other should be a requirement before we include them in the final
> version of the spec. If proposal A is adopted or status quo prevails,
> please record this as one of the CR exit criteria.
> 
> 
Received on Saturday, 28 May 2005 22:04:49 GMT

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