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Re: 'initiate' flag issue

From: Kohei Honda <kohei@dcs.qmul.ac.uk>
Date: Mon, 30 Oct 2006 16:45:38 +0000
Message-ID: <45462C32.4050907@dcs.qmul.ac.uk>
To: Yves Lafon <ylafon@w3.org>
CC: Martin Chapman <martin.chapman@oracle.com>, 'Gary Brown' <gary@pi4tech.com>, 'WS-Choreography List' <public-ws-chor@w3.org>

My apologies I came back to this two weeks later. I just realised these 
mails.

I do not know the initial motivation for this flag. Anyway here I note 
how we can
use it. I am sorry I am presenting it now, but I am getting some ideas 
about the use
and theory of CDL better than before, and that is giving me additional 
ideas.

Having initial flag combined with the (automatically filled) primary 
session identity
is in fact very useful. That gives a flexible mechanism to extract a 
series of interactions
from a given description and further associate a clear-cut idea of type.

Suppose Alice asks Bob three times, each with initiation flag. Suppose, 
to the
same channel, Carol asks Bob twice, each with initiation flag.

If these interactions are all (say) askQuote followed by thisIsQuote, 
then this means
Bob does not have to offer "two repeated interactions" and "three 
repeated interactions"
separately to Alice and Carol. It only offers one kind of interaction, 
repeatedly offered
to anybody who invokes Bob. If this is totally nested, we can use 
perform. But suppose
two of these interactions (especially assuming each is in fact 
containing a series of many
communications) interleave with each other. Then we cannot use perform.

Because of loops and multiple participants in loops, this can become 
arbitrarily complex.
It can be disentangled if we are clear about different sessions --- 
where each begin,
to which session each message belongs to, etc.

*Practically* this means the following:

If we have this flag, and if we have co-relation identity (as is called 
now), then
we can have a very clean type structure and EPP mapping.

If this is harmless otherwise, therefore, I propose to keep it.

kohei

Yves Lafon wrote:
>
> On Tue, 17 Oct 2006, Martin Chapman wrote:
>
>>
>> I very much agree with the reuse argument to remove the flag; a 
>> choreo will
>> be far more resusable if the flag doesn't exist, or at least add a
>> donít'care/maybe option!
>
> I concur, In fact, the best, if this distinction is needed would be an 
> initiate element somewhere (like on a description of the root choreo) 
> with a link to the initiating interaction. But not something inside 
> the choreo definition.
>
>>
>> Martin.
>>
>>> -----Original Message-----
>>> From: public-ws-chor-request@w3.org
>>> [mailto:public-ws-chor-request@w3.org] On Behalf Of Gary Brown
>>> Sent: Tuesday, October 17, 2006 9:04 PM
>>> To: 'WS-Choreography List'
>>> Subject: 'initiate' flag issue
>>>
>>>
>>>
>>> Hi
>>>
>>> Thanks to Yves, I have found Nick's comments on my original
>>> proposal for
>>> removing the initiate flag:
>>> http://lists.w3.org/Archives/Public/public-ws-chor/2004Oct/0049.html
>>>
>>> Nick's argument focused on the declarative flag helping a
>>> designer when
>>> composing choreographies. However, I don't see this as being a
>>> compelling argument - in fact, it is better from a reuse point of view
>>> that previously standalone choreographies that initiated a
>>> choreography
>>> session are able to be composed into more comprehensive choreography
>>> which now starts the session at a different point.
>>>
>>> Regards
>>> Gary
>>>
>>>
>>>
>>>
>>
>>
>>
>
Received on Monday, 30 October 2006 16:45:58 GMT

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