RE: [wsbpel] Issue 6.2 - Updated Proposal For Vote

["Trickovic, Ivana" <ivana.trickovic@sap.com>]

  Hi Chris,

#1: How about to add in (5) the following:
"... a completionCondition
element the completion condition is evaluated each time AFTER a directly
enclosed activity completes."

> It would seem better if the expression was evaluated once prior to the flow executing.
What does is mean "prior to the flow executing"? How does that work because multiple activities are started in parallel. 

#2: You are right. How about the following:
"If all directly enclosed activities have been completed
but the completion condition evaluates to false the
"bpws:completionConditionFailure" MUST be thrown by the flow/parallel forEach activity."

#3: The current proposal is inline with section 13.4.4. But we may discuss this on the call and you may propose an amendment. Would that be ok for you?

#4: Any suggestion? 

Thanks,

Ivana

-----Original Message-----
From: Chris Keller
To: Trickovic, Ivana; wsbpel@lists.oasis-open.org
Cc: alex.yiu@oracle.com
Sent: 14.09.2005 18:14
Subject: RE: [wsbpel] Issue 6.2 - Updated Proposal For Vote

Hi Ivana,

 

Some questions/comments:

 

1. Is the branches expression evaluated each time a directly enclosed
activity completes or is the test evaluated each time?  It is unclear in
your description below.  It would seem better if the expression was
evaluated once prior to the flow executing.

 

2. What happens if the flow or parallel forEach completes, but the
completion condition is not met?

 

3. If this is adopted we would also have to change section 13.4.4
Semantics of Activity Termination from:

 "However, a termination handler cannot throw any fault. Even if an
uncaught fault occurs during its behavior, it is not rethrown to the
next enclosing scope. This is because the enclosing scope has already
either faulted or is in the process of being terminated, which is what
is causing the forced termination of the nested scope."

to just:

 "However, a termination handler cannot throw any fault. Even if an
uncaught fault occurs during its behavior, it is not rethrown to the
next enclosing scope."

 

4. Is branches the most suitable name for the element name?

 

Regards,

Chris Keller

 

 

Regards,

Chris

 

 

 

  _____  

From: Trickovic, Ivana [mailto:ivana.trickovic@sap.com] 
Sent: Wednesday, September 14, 2005 3:15 AM
To: wsbpel@lists.oasis-open.org
Cc: alex.yiu@oracle.com
Subject: [wsbpel] Issue 6.2 - Updated Proposal For Vote

 

Below please find an updated proposal for issue 6.2.

 

Kind regards,

 

Ivana

 

 

 

Issue 6.2: Updated proposal: 
Last modified: Sept 13, 2005 - 23:30 PDT 


Motivation 
===========

The current semantics of the flow activity is that it completes when all
its (directly) enclosed activities have completed, either successfully
or unsuccessfully. However, there are scenarios where it is necessary to
have ability to (successfully) complete the flow activity before all its
directly enclosed activities complete in order to speed up the process
execution. 

The completion condition may have different flavors:
(1) Wait for N out of M nested activities to complete
(2) Wait until after boolean condition C evaluates to true

This updated proposal is restricted to case (1). 

The completion condition is interesting for the flow activity and for
the parallel forEach activity.


Proposal 
=========

Syntax:

<flow standard-attributes>
standard-elements
      <links>?
         <link name="ncname">+
      </links>
      <completionCondition>?
      activity+
</flow>


<forEach counterName="ncname" ...>
     standard-elements
     <iterator>
        <startCounterValue expressionLanguage="anyURI">
           ...
        </startCounterValue>?
        <finalCounterValue expressionLanguage="anyURI">
           ...
        </finalCounterValue>?
     </iterator>
     <completionCondition>?
     Scope
</foreach>


<completionCondition extension-attribute>
      extension-element
      <branches expressionLanguage="URI"?
countCompletedBranchesOnly="yes|no"?>
          an-integer-expression
      </branches>
</completionCondition>


Semantics:

(1) The completionCondition element is an optional element of the flow
activity and the parallel forEach activity. Default behavior of the flow
activity and the parallel forEach activity is they wait for all their
directly enclosed activities to complete. Optional <completionCondition>
is applicable to parallel forEach only, and not serial forEach. This
restriction MUST be enforced by static analysis. 

(2) <branches> is an integer value expression which is used to define
condition of flavor N out of M. It is evaluated at the end of execution
of each directly enclosed activity. This condition has "at least N out
of M" semantics. (The exact N out of M condition semantics involve
resolving racing condition among directly enclosed activities.)

(3) If the integer value is larger than the number of directly enclosed
activities, then bpws:invalidBranchCondition fault MUST be thrown. Note
that the number of branches may be known only during runtime in some
cases. Static analysis should be encouraged to detect this erroneous
situation at design time when possible. (For example, when the branches
expression is a constant.)

(4) Element <branches> has an optional attribute
"countCompletedBranchesOnly". Its default value is "no". If
countCompletedBranchesOnly is "no", it means the BPEL processor will
count branches which have completed (either successfully or
unsuccessfully). If countCompletedBranchesOnly is "yes", it means the
BPEL processor will count branches which have completed successfully
only.

(5) If flow/parallel forEach activity specifies a completionCondition
element the completion condition is evaluated each time a directly
enclosed activity completes. If the completion condition evaluates to
true the flow/parallel forEach activity completes successfully. All
still running directly enclosed activities will be terminated. This
means that the flow/parallel forEach activity begins implicitly
terminating the directly enclosed activities that are still active.

(6) Standard BPEL termination semantics applies to running directly
enclosed activities when the completion condition is met. The
termination of running nested activities follows the termination
semantics defined in the specification (see section 13.4.4 Semantics of
Activity Termination). 

(end)
----------------