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Re: Clarifying exchange type

From: Kohei Honda <kohei@dcs.qmul.ac.uk>
Date: Mon, 30 Oct 2006 20:30:38 +0000
Message-ID: <454660EE.2010700@dcs.qmul.ac.uk>
To: Gary Brown <gary@pi4tech.com>
CC: "Monica J. Martin" <Monica.Martin@Sun.COM>, Martin Chapman <martin.chapman@oracle.com>, 'WS-Choreography List' <public-ws-chor@w3.org>

Hi Gary,

Well that I feared. Co-relation identity is not part of the type 
structure but part of application
data. I think this cannot be changed now. I am sorry I could not predict 
this at the initial

Anyway here is a concrete situation where such identity (at least a 
basic one) is better be
as part of type structure, part of a header, something users cannot 

Suppose we send a channel (which means we delegate a session to somebody 
in practice).
Since the identity is just part of a message content, we do not have an 
automatic scheme to
send this identity together. We do not have to do it. So it is not 
ensured that identity is
preserved --- if we wish to do it. Of course we can always do this in an 
ad hoc manner,
but the issue is we cannot guarantee the identity of a series of 

So generally, at least some part of identities should be part of 
"message header", something
which users cannot manipulate and part of the interaction structure 
(hence that which can
be type abstracted). No other web languages have it, so I think we 
should leave this as it is.

As I wrote, my point is that this is the general way to treat such 
protocols, *not* we should
do this for this particular instance. The generality is that we can deal 
with arbitrarily inserted
actions between request and return, and still can keep the correspondence.

So this would be for future.

Best wishes,


Gary Brown wrote:
> Hi Kohei
> I don't think co-relation can be used as this would be dependent upon 
> the contents of the messages, which cannot be relied upon to be 
> distinct from a previous request. So I think the most appropriate 
> approach is the new exchange action type, which makes it then 
> consistent with the way other Message Exchange Patterns are described 
> (i.e. explicitly).
> Regards
> Gary
> Kohei Honda wrote:
>> A bit confused with negation:
>>> From this viewpoint, my question is: are there any these 
>>> "request-reply" and its variants, including
>>> notifications, which cannot be captured as a pattern of interaction, 
>>> which can be made explicit by the
>>> use of  co-relation identity?
>> I meant, in the last clause: ..., which cannot be made explicit by 
>> the use of co-relation identity?
>> My question was, therefore: whether all can be captured by 
>> co-relation (or session) identities or not.
>> As written, even if all can, I do not oppose having explicit 
>> constructs for specifying local (or micro)
>> protocols.
>> kohei
Received on Monday, 30 October 2006 20:30:51 UTC

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