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Re: WSDL 1.2 drops use="encoded"

From: Simon Fell <soap@zaks.demon.co.uk>
Date: Mon, 24 Feb 2003 19:17:28 -0800
To: xml-dist-app@w3.org
Message-ID: <bhnl5vofelqpf04e3a44un4im91h88msl0@4ax.com>

I thought that the requirements detailed in R028 would require the
description of SOAP encoded messages.

Whilst I understand the interop issues around encoded messages, and
why you'd want to avoid it, shouldn't that be resolved at the SOAP
level ?
I'm concerned that if WSDL ends up being able to describe only a
subset of valid SOAP messages, all that means is yet another format
will appear to describe the set of messages WSDL can't describe.


On Mon, 24 Feb 2003 14:29:58 -0800, in soap you wrote:

>The WS Description WG wanted to point out a change we made to WSDL 1.2
>that changes the way messages that use SOAP Encoding are described, and
>solicit your reaction.  The "use" attribute on WSDL 1.2's <soap:body>
>element has been dropped.  The rationale (compiled by Arthur Ryman of
>IBM) follows.
>The WSDL 1.1 SOAP binding currently has a use attribute which can take
>the values literal and encoded. The use attribute interacts with the
>encodingStyle attribute. The cases are as follows:
>1. use="literal", encodingStyle="". The SOAP message is exactly as
>described by its XML schema, but nothing is claimed about how the schema
>was derived.
>2. use="literal", encodingStyle="some-URI". The SOAP message is exactly
>as described by its XML schema and the schema was derived using the
>encoding algorithm identified by some-URI. The writer of the message is
>required to create it exactly as described by the schema. The knowledge
>of the encoding algorithm can be exploited by tools that might generate
>a data structure from the schema. The main example here is SOAP
>encoding. WS-I.org is defining a new algorithm for object graphs.
>3. use="encoded", encodingStyle="some-URI". The SOAP message is not
>necessarily as described by the XML schema which was derived using the
>encoding algorithm identified by some-URI. There may be variants in the
>message not described in the schema. The reader of the message is
>required to understand all variants. For example, in SOAP encoding,
>element content can appear inline or via reference (e.g. for
>multi-reference objects).
>4. use="encoded", encodingStyle="". This case is not allowed. If the
>SOAP message is encoded then there must be an encoding style.
>WS-I.org has studied interoperability problems and has come to the
>conclusion that only use="literal" should be used where interoperability
>is required. Since interoperability is one of the main features of Web
>services, it seems reasonable to follow this recommendation in WSDL 1.2.
>This recommendation does not really restrict the message content. It
>only restricts how the message is described in WSDL. Case #3 is
>disallowed. This places the burden on the Web service implementor to
>describe the messages exactly.
>In many cases, SOAP encoding can be described by an accurate schema,
>e.g. if the data is tree like. Also, the new WS-I.org proposal for
>encoding object graphs does have accurate schemas. It is therefore not
>necessary to remove the encodingStyle attribute since this is a valuable
>hint to tools. However, if only use="literal" is supported, then the use
>attribute can be safely dropped.
Received on Monday, 24 February 2003 22:17:10 UTC

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