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Re: Issue LC50 - MEPs

From: Amelia A Lewis <alewis@tibco.com>
Date: Thu, 18 Nov 2004 12:34:25 -0500
To: David Booth <dbooth@w3.org>
Cc: jeffsch@windows.microsoft.com, mgudgin@microsoft.com, sanjiva@watson.ibm.com, gdaniels@macromedia.com, www-ws-desc@w3.org
Message-id: <20041118123425.20fd9a89.alewis@tibco.com>

It is my understanding of the current status quo, which is based on the
combination of WSDL 1.1 and WS-Addressing, that features/extension
specs/policies can override the semantic of a MEP.  I don't like this,
mind, but I believe that this is the status quo.

A cleaner semantic would require that, if the response in an in-out is
sent to an alternate address, or even to an address specified by a
feature/policy/extension spec, a different MEP (David's horribly
confusingly-named p2c (sorry, David)) be used.

The implication is that a binding to, for instance, internet email for
the current in-out *requires* that the reply-to header always be set to
the address of the originating node.  In order to have the flexibility
to send to a different node, one would want to have a more general
in-out MEP, one which specifically permits redirection of the response.

I *strongly* disagree with Glen's assertion that the client doesn't
care, that the client views this as "two one-way" (probably meant to be
"in-only" plus "out-only", but it isn't true, in my opinion, anyway). 
The client *ought* to be able to know, in advance, whether it's expected
to supply an address for a response, and ought to be able to vary its
requests such that it can receive responses itself, or direct them
elsewhere.  All of this information is of interest to the requesting
node (as well as to the target node for the response, which presumably
also has access to the WSDL).

Amy!
On Thu, 18 Nov 2004 12:18:34 -0500
David Booth <dbooth@w3.org> wrote:

> Jeffrey/Gudge and Amy,
> 
> At the WSDL 2.0 F2F meeting last week, we discussed the MEP issue that
> I had raised:
> http://www.w3.org/2002/ws/desc/4/lc-issues/issues.html#LC50
> I had proposed adding an MEP (similar to p2c in 
> http://dev.w3.org/cvsweb/~checkout~/2002/ws/desc/wsdl12/meps-vs-iops/meps-vs-iops_clean.htm#p2c
> or http://tinyurl.com/4pjo4 ) that would not require the response
> message to go back to the original requester.  (At present, our in-out
> pattern is essentially p2e:
> http://dev.w3.org/cvsweb/~checkout~/2002/ws/desc/wsdl12/meps-vs-iops/meps-vs-iops_clean.htm#p2e
> , which is a specialization of p2c.  I.e., p2c is more general or
> less constrained than p2e.)
> 
> Sanjiva argued that the response is still going back to the requester
> even if it is diverted to a different physical location.  In other 
> words, it is still the same requester node even if the message is
> being sent to a different physical address.  
> 
> I think this is a reasonable viewpoint.  I am slightly worried that
> there could be other undiscovered issues if an underlying addressing
> mechanism has the ability to send the message to an arbitrary
> recipient that could in fact be a *different* node, but I haven't yet
> thought of any.
> 
> GlenD also pointed out that from the client's point of view, if the
> response is *not* going back to the same (logical) requester, then
> from the client's point of view, p2c is equivalent to using two
> one-way patterns (one going in, the other going out).  
> 
> Since a WSDL document 
> should only contain information that is needed by *both*
> the service and the client, I think Glen's point is compelling.
> However, I seem to remember that both of you were strong proponents 
> of the WG adopting adopting the more general (less constrained)
> pattern (such as p2c) instead of p2e, so I would like to hear your
> view of this issue before I rescind my proposal to add p2c.
> 
> -- 
> 
> David Booth
> W3C Fellow / Hewlett-Packard
> 


-- 
Amelia A. Lewis
Senior Architect
TIBCO/Extensibility, Inc.
alewis@tibco.com
Received on Thursday, 18 November 2004 17:34:54 GMT

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