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RE: Issue 1108 - proposal

From: Martin Chapman <martin.chapman@oracle.com>
Date: Tue, 21 Jun 2005 11:47:00 +0100
To: "'Gary Brown'" <gary@pi4tech.com>, "'Steve Ross-Talbot'" <steve@pi4tech.com>, "'WS-Choreography List'" <public-ws-chor@w3.org>
Message-ID: <000001c5764e$90ab28b0$0901a8c0@ie.oracle.com>

Gary I cant find any mention of 1108 in the f2f minute

>-----Original Message-----
>From: public-ws-chor-request@w3.org 
>[mailto:public-ws-chor-request@w3.org] On Behalf Of Gary Brown
>Sent: Tuesday, June 21, 2005 9:36 AM
>To: Martin Chapman; 'Steve Ross-Talbot'; 'WS-Choreography List'
>Subject: Re: Issue 1108 - proposal
>
>
>
>Hi Martin,
>
>This was discussed at the f2f and I thought it was agreed that 
>the proposal 
>would be adopted.
>
>The only objection at the time from Nick was that he thought 
>BPEL did it the 
>same way as the current approach in CDL, but then when we 
>checked, it was 
>found that BPEL was inline with approach outlined in the proposal.
>
>Regards
>Gary
>
>----- Original Message ----- 
>From: "Martin Chapman" <martin.chapman@oracle.com>
>To: "'Steve Ross-Talbot'" <steve@pi4tech.com>; 
>"'WS-Choreography List'" 
><public-ws-chor@w3.org>
>Sent: Monday, June 20, 2005 10:18 PM
>Subject: RE: Issue 1108 - proposal
>
>
>
>For some reason this seems to have fallen through the cracks 
>so lets put it on next weeks agenda.
>
>Martin.
>
>>-----Original Message-----
>>From: public-ws-chor-request@w3.org 
>>[mailto:public-ws-chor-request@w3.org] On Behalf Of Steve Ross-Talbot
>>Sent: Tuesday, May 10, 2005 6:46 PM
>>To: 'WS-Choreography List'
>>Subject: Issue 1108 - proposal
>>
>>
>>
>>Martin,
>>
>>here is a possible way forward.
>>
>>Cheers
>>
>>Steve T
>>
>>Begin forwarded message:
>>
>>> Resent-From: public-ws-chor@w3.org
>>> From: "Gary Brown" <gary@pi4tech.com>
>>> Date: 20 April 2005 09:13:02 BST
>>> To: <public-ws-chor@w3.org>
>>> Subject: PROPOSAL related to: Example showing problem with current 
>>> isolation semantics in CDL
>>>
>>> We should clearly state in the spec that nested isolation 
>>> choreographies are not permitted.
>>>
>>> Proposed Text:
>>>
>>> Section 2.4.5 contains the following bullet point:
>>>
>>> " When isolation is set to "true", changes to the Variable
>>information
>>> MUST be visible for read or for write to its sibling Choreographies 
>>> only after this Choreography has completed "
>>>
>>> This should be extended to include the text:
>>>
>>> "An isolated choreography cannot directly or indirectly perform 
>>> another isolated choreography."
>>>
>>> Regards
>>> Gary
>>>
>>> ----- Original Message -----
>>>  From: Gary Brown
>>> To: public-ws-chor@w3.org
>>> Sent: Tuesday, April 19, 2005 12:56 PM
>>> Subject: Example showing problem with current isolation 
>semantics in 
>>> CDL
>>>
>>> Hi
>>>
>>> After the recent discussion on isolation being inherited from the 
>>> enclosing choreography, I wanted to outline the following 
>example to 
>>> show how simply changing the isolation attribute of an enclosing 
>>> choreography can significantly change the behavior of the 
>>> choreography.
>>>
>>> <choreo A>
>>>
>>> <variable name="var1" />
>>>  <variable name="var2" />
>>> <choreo B isolation=true >
>>>
>>> <assign value "x" to "var1" />
>>>  <assign value "x" to "var2" />
>>> </choreo>
>>> <choreo C isolation=true >
>>>
>>>  <assign value "y" to "var1" />
>>>  <assign value "y" to "var2" />
>>> </choreo>
>>>
>>> <parallel>
>>> <perform choreo B>
>>> <bind var1/>
>>> <bind var2/>
>>> </perform>
>>>
>>> <perform choreo C>
>>> <bind var1/>
>>> <bind var2/>
>>> </perform>
>>> </parallel>
>>> </choreo>
>>>
>>> If choreo A is not isolated, then choreo B and C are
>>isolated in their
>>> own right - and therefore because they are both accessing common 
>>> variables, I assume that one or the other of the performs will wait 
>>> until the other has completed - so in fact they will be 
>performed in 
>>> sequence. [If this assumption is not true, then I need to have an 
>>> explanation of the behavior when two sub-choreos have the same 
>>> isolated variable - at what point do they wait?]
>>>
>>> Therefore the result would be that both variables would 
>have the same 
>>> value - either 'x' or 'y' depending on the order in which the 
>>> sub-choreos were actually performed.
>>>
>>> However, if we now make choreo A isolated, the isolated
>>attribute on B
>>> and C is now ignored, as the isolation is inherited from the parent 
>>> choreography (as described at the last f2f).
>>>
>>> This now means that because the variables 'var1' and 'var2'
>>are within
>>> the same isolation scope, when the two sub-choreos are performed, 
>>> there is no waiting/blocking. This means that the result of the 
>>> overall choreography is non-deterministic, the variables could have 
>>> any combination of 'x' or 'y'.
>>>
>>> The problem is that a sub-choreography may be defined on 
>the basis of 
>>> having isolation semantics - and this is effectively 
>overridden when 
>>> performed from an already isolated choreography. Whereas if nested 
>>> isolation was supported, the semantics of the
>>sub-choreographies would
>>> be preserved, regardless of the isolation status of the enclosing 
>>> choreography.
>>>
>>> This example is showing a simple example, but in a real example the 
>>> isolation of a top level choreography could have unforeseen 
>>> consequences on a sub-choreography that is many levels of nesting 
>>> removed from the isolated choreography. A case of a small change 
>>> having a significant impact on bahavior.
>>>
>>> Regards
>>> Gary
>>
>>
>>
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Received on Tuesday, 21 June 2005 10:46:33 UTC

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