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Re: What WSDL defines - the diagram!

From: David Booth <dbooth@w3.org>
Date: Thu, 06 Nov 2003 01:50:44 -0500
Message-Id: <>
To: Anne Thomas Manes <anne@manes.net>, Mark Baker <distobj@acm.org>
Cc: www-ws-desc@w3.org, paul.downey@bt.com

P.S. The greater significance of the diagram is not so much in what it 
includes but what it omits.  In particular, it says nothing about what a 
WSDL *processor* must or must not do.

There are different types of interoperability that we could potentially 
strive to obtain with the WSDL 2.0 spec, which I'll arbitrarily call:

Type 1: Web Service & Client interop.  This type of interop is to ensure 
that the WS and client agree on the mechanics of their interaction -- the 
message formats, data types, transport, MEP, etc.  (Of course, they still 
need to use other means to ensure that they agree on the semantics and 
other higher-level details of the interaction -- beyond what WSDL covers.)

Type 2: WSDL Processor interop.  This type of interop would ensure that 
different WSDL processors would have the same behavior when presented with 
a given WSD.

WSDL 2.0 pursues type 1: Web Service & Client interop.  It does not define 
what a WSDL processor must or must not do with a given WSD.  (And rightly 
so, in my opinion: what a processor *does* with a given WSD is its own 
business -- not ours.)

At 01:10 PM 11/5/2003 -0500, David Booth wrote:

>Mark & Anne,
>Certainly, a WSDL document does not *fully* define client or service 
>behavior, but it does *partially* define their behavior.  That's what MEPs 
>are all about.  When a WSDL document specifies a message exchange pattern, 
>that pattern partially defines the behavior of the interacting parties -- 
>not their internal behavior, but their externally observable behavior, 
>i.e., what messages they send and receive and in what sequence.
>The labels on the diagram were somewhat abbreviated, and omitted the word 
>"partially".  A clearer diagram is at
>At 01:34 PM 11/4/2003 -0500, Anne Thomas Manes wrote:
>>WSDL explicitly does not define client or service behaviour. It describes 
>>syntax of messages and protocols used to exchange those messages.
>>At 10:41 AM 11/4/2003, Mark Baker wrote:
>>>Cool, thanks for tackling that at the f2f.
>>>But I disagree with the diagram.  As it was explained to me, a WSDL 2.0
>>>document could be said to "describe the syntax" of client and service
>>>("schema in, schema out"), rather than "define the behaviour", which
>>>would require defining what in/out means in relation to any requested
>>>semantics (aka the protocol).
>>>WSDL 1.1 describes the protocol in that it suggests that a successful
>>>response to a message means that the requested operation in the message
>>>was successfully invoked.  WSDL 2.0 is ambiguous.
>>>Mark Baker.   Ottawa, Ontario, CANADA.        http://www.markbaker.ca
>David Booth
>W3C Fellow / Hewlett-Packard
>Telephone: +1.617.253.1273

David Booth
W3C Fellow / Hewlett-Packard
Telephone: +1.617.253.1273
Received on Thursday, 6 November 2003 11:54:20 UTC

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