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Re: Issue 1108 - proposal

From: Steve Ross-Talbot <steve@pi4tech.com>
Date: Mon, 27 Jun 2005 08:28:45 +0100
Message-Id: <27a2c9bfa876cfe3faf639fbf2348976@pi4tech.com>
Cc: "'Gary Brown'" <gary@pi4tech.com>, "'WS-Choreography List'" <public-ws-chor@w3.org>
To: "Martin Chapman" <martin.chapman@oracle.com>

The bugzilla entry for 1108 says:

"When an isolated sub-choreography terminates unsuccessfully, does this 
mean that
any changes made to variables bound from its parent choreography are 
made
visible - or are they discarded.

The text in 2.4.5 only talks about the variables being made visible for 
read and
write after the choreo has completed - but does not indicate whether 
that only
means successful completion."

The resolution for 1459 states:

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."

I would have thought that this closes 1108 also.

Cheers

Steve T


On 21 Jun 2005, at 11:55, Martin Chapman wrote:

>
> ignore previous, hit send key premature - must be a fat finger day.
>
> Gary,
>
> I can't find any mention of 1108 in the minutes/irc log. It also wasn't
> on
> the agenda or on my outstanding issues list.
>
> The only discussion on isolation was issue 1459, and we should verify
> whether
> that resolution also resolves 1108 (or verify that 1108 is a dupl of
> 1459).
>
>
> Martin.
>
>
>> -----Original Message-----
>> From: Martin Chapman [mailto:martin.chapman@oracle.com]
>> Sent: Tuesday, June 21, 2005 11:47 AM
>> To: 'Gary Brown'; 'Steve Ross-Talbot'; 'WS-Choreography List'
>> Subject: RE: Issue 1108 - proposal
>>
>>
>> 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
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>
>
>
>
>
Received on Monday, 27 June 2005 07:28:57 GMT

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