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Subject: RE: [wsbpel] Issue 27 - Proposal to vote - Setting link status in case of transitioncondition


Assaf,

As Ron points out, the setting of link status is meaningful only after
the evaluation of the transition condition is completed.  When a fault
occurs in the scope within which the condition is to be evaluated,
before the evaluation of the condition is complete, the link status is
always set to false.  This is quite independent of the nature and source
of the fault, and there is nothing special about the faults that may
occur within transition conditions as far as this rule is concerned.
Again, this matters only when the corresponding link is leaving the
scope that faulted.

I would not exactly say that "the transition condition is always
evaluated by the enclosing construct" although the idea is correct.
Conditions are not evaluated by a construct.  I think the most
meaningful thing to say is that "transition conditions are evaluated in
the scope immediately enclosing the source activity of a link".

Satish

-----Original Message-----
From: Assaf Arkin [mailto:arkin@intalio.com] 
Sent: Saturday, October 18, 2003 6:43 PM
To: Satish Thatte
Cc: Ron Ten-Hove; wsbpel@lists.oasis-open.org
Subject: Re: [wsbpel] Issue 27 - Proposal to vote - Setting link status
in case of transitioncondition

Would it be fair to say that the transition condition is always 
evaluated by the enclosing construct?

In other words, if activity X is a source activity and has a transition 
condition, and is encapsulated by activity Y, then activity Y is in fact

responsible to evaluate the transation condition using the variables 
accessible in its scope and throw a fault if the transition condition 
fails? An enclosing construct may also refuse to evaluate any transition

conditions (e.g. a while activity or an event handler).

Another point that I don't think was answered so far is what happens 
when there are two transition conditions and a fault occurs when 
evaluating one of them? Are both of them set to false, or only the one 
that generated a fault? I believe for consistency both of the links 
should have their status set to false.

arkin

Satish Thatte wrote:

> You are right, my sentence is misleading.  The link status is false 
> because of the fault not because the transition condition is not yet 
> evaluated.  Thanks for the correction.  Incidentally, the link status 
> matters only if the link target is outside the scope that faulted.
>
>  
>
>
------------------------------------------------------------------------
>
> *From:* Ron Ten-Hove [mailto:Ronald.Ten-Hove@Sun.COM]
> *Sent:* Friday, October 17, 2003 1:22 PM
> *To:* Satish Thatte
> *Cc:* wsbpel@lists.oasis-open.org
> *Subject:* Re: [wsbpel] Issue 27 - Proposal to vote - Setting link 
> status in case of transitioncondition
>
>  
>
> Satish Thatte wrote:
>
> The link status issue is really more general than this as Goran 
> pointed out during the call.  A scope can always fault in an unrelated

> place while one or more transition conditions within it are being 
> evaluated, in this case, transition conditions on other links sourced 
> at the same source scope.  It is impossible to specify the exact 
> behavior in such races in the presence of true (multi-processor) 
> concurrency.  If the evaluation of the conditions is not complete 
> (i.e., the link has not actually set its status) then the link status 
> is False.  In the case of the fault occurring in the evaluation of the

> transition condition itself the evaluation of the condition is not 
> complete and therefore the link status is False.
>
> My understanding is that links are tri-state: empty, true, or false. 
> Until the transition condition is evaluated, the link remains marked 
> as empty, not false as you suggested. Faulting the scope should case 
> the link given in this case to marked as false, as part of dead-path 
> elimination.
>
> -Ron
>
>  
>
>  
>
>
------------------------------------------------------------------------
>
> *From:* Prasad Yendluri [mailto:pyendluri@webmethods.com]
> *Sent:* Thursday, October 16, 2003 3:48 PM
> *To:* Ashwini Surpur; Assaf Arkin
> *Cc:* wsbpel@lists.oasis-open.org <mailto:wsbpel@lists.oasis-open.org>
> *Subject:* Re: [wsbpel] Issue 27 - Proposal to vote - Setting link 
> status in case of transitioncondition
>
>  
>
> True. This aspect was clarified in the discussions related to this 
> issue but did not make into the
> proposed resolution (we voted on!).
>
> I also see the need to address what the status of the link ends up 
> being in this scenario. The
> obvious answer seems to that "a transition condition evaluation error 
> would be same as the
> transition condition having evaluated to 'not ture'/false'." But, I 
> somehow feel some will not
> see it this way. In any case we need to make a definitive statement 
> here and not leave a
> loose end dangling.
>
> Regards, Prasad
>
> -------- Original Message --------
>
> *Subject: *
>
> 	
>
> Re: [wsbpel] Issue 27 - Proposal to vote - Setting link status in case

> of transitioncondition
>
> *Date: *
>
> 	
>
> Thu, 16 Oct 2003 13:18:25 -0700
>
> *From: *
>
> 	
>
> Ashwini Surpur <ashwini.surpur@oracle.com> 
> <mailto:ashwini.surpur@oracle.com>
>
> *Organization: *
>
> 	
>
> Oracle Corporation
>
> *To: *
>
> 	
>
> Assaf Arkin <arkin@intalio.com> <mailto:arkin@intalio.com>
>
> *CC: *
>
> 	
>
> wsbpel@lists.oasis-open.org <mailto:wsbpel@lists.oasis-open.org>
>
>  
>
>Also from the discussion on issue 27 I get that the local variables of
the scope 
>
>cannot be used to evaluate the transition condition of the links and
only the 
>
>variables of the parent scope should be used. This needs to be
documented 
>
>explicitly as well.
>
> 
>
>-Ashwini
>
> 
>
>Assaf Arkin wrote:
>
> 
>
>> Proposal to resolve issue 27 by adding the following paragraph to the
>
>> specification in the description of how links are handled (pages
64/65):
>
>> 
>
>> Note that the transition condition is evaluated after the activity
has
>
>> completed. If an error occurs while evaluating the transition
condition,
>
>> that error does not affect the completion status of the activity and
is
>
>> handled by the activity's enclosing scope. In the case of
>
>> scopes, completion does not necessarily imply successful completion.
A
>
>> scope may suffer an internal fault and yet complete (unsuccessfully)
if
>
>> there is a corresponding fault handler associated with the scope and
>
>> that fault handler completes without throwing a fault.
>
>> 
>
>> arkin
>
>> 
>
>> (This is the same proposal sent on Sep 30, resent for your
convenience)
>
>  
>
> 
>
>
>
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