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Re: Two logical WSDL documents describing the same service

From: David Booth <dbooth@w3.org>
Date: Thu, 08 Jan 2004 09:25:18 -0500
Message-Id: <5.1.0.14.2.20040108083415.02194da8@localhost>
To: Amelia A Lewis <alewis@tibco.com>, paul.downey@bt.com,
Cc: www-ws-desc@w3.org

At 11:06 AM 12/18/2003 -0500, Amelia A Lewis wrote:
>. . .
>I think that multiple incompatible interfaces, as described in David
>Booth's proposal, are equivalent to multiple incompatible schemata,
>which, in David Orchard's article, requires a change of namespace.

They are not necessarily incompatible, even if they are very different.  If 
you have two logical WSDL documents[1] defining different interfaces for 
the same service and service endpoint, and for some reason you consider 
them together, they could be ambiguous in the sense that it may not be 
possible to discern which interface a particular message is intended 
for.  However, we've already decided that uniqueness on the wire is the 
application's problem -- not ours.  As pointed out, this may be the 
explicit intent (for versioning).

On the other hand, the two interfaces may be very different in the sense 
that it will always be syntactically obvious which interface a given 
message is intended for.  In this case, these interfaces would be 
"incompatible" in a narrow sense: If your software has no concept of two 
two different interfaces for the same service, then it would be hopelessly 
confused.  (This would presumably be the case for most WSDL processors.)

However, if your software is for some reason doing something different, and 
is simultaneously considering multiple logical WSDL documents, then it may 
well understand that two logical WSDL documents with very different 
interfaces could be describing the same service, and those interfaces might 
(for example) represent different facets of the same service.

The WSDL spec can reasonably only define the meaning of a single sentence 
in the WSDL language.  The meaning of two sentences considered together is 
not something that the WSDL language can (or should) define.  So although 
one person may view those two interfaces as representing "different facets 
of the same service", someone else may legitimately view them as 
representing something else.

[1] By "logical WSDL document" I mean the set of components denoted by a 
single physical WSDL document after following imports/includes, etc.  I.e., 
a single sentence in the WSDL language.   For further explanation see:
http://lists.w3.org/Archives/Public/www-ws-desc/2003Nov/0085.html


-- 
David Booth
W3C Fellow / Hewlett-Packard
Telephone: +1.617.253.1273
Received on Thursday, 8 January 2004 10:02:52 GMT

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