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From Jit K <jkf...@gmail.com>
Subject Re: Dynamically invoke a child process
Date Thu, 03 Nov 2016 04:49:18 GMT
Hi Sathwik,

>> In BPEL a sub-process is implemented by using a <SCOPE /> within the
<PROCESS />. Just to clarify your sub process definition is actually a full
blown process. Am I right?
Yes, my sub process is a full blown process (defined in a separate .bpel
file).

I am restructuring my query about While loop. I am considering explicit
correlations to implement this because we will have to relate
invoke-receive activities.
While loop executes its child activity in sequence, i.e. start new activity
after first is complete. This is OK for one way <invoke>. However I do not
understand how it will work for <receive>. Considering the sequential
behavior of while loop, in the first iteration it will execute the first
<receive> activity and wait till it is complete. Once the first <receive>
is complete, it will execute the second <receive> and wait till is is
complete and so on. However, while it is waiting for second <receive>, what
if the process receives a response from 3rd <invoke>? It will fail because
there is no corresponding <receive> on.
Is my understanding correct or I am missing something here?

Regards,
JK


On Wed, Nov 2, 2016 at 6:46 PM, Sathwik B P <sathwik.bp@gmail.com> wrote:

> Response Inline
>
> On Wed, Nov 2, 2016 at 4:50 PM, Jit K <jkfrm8@gmail.com> wrote:
>
> > Hi Sathwik,
> >
> > Thank you for taking time to suggest these ideas.
> >
> > I was thinking on the same line but did not implement because I was not
> > sure about calling <receive /> in a loop.
> > Since <receive /> is a blocking activity, I thought the loop will stop
> > during the first iteration when it executes the first <receive />
> activity
> > and will not not complete.
> >
> > I have few queries.
> >
> > 1) Iterative forEach parallel='yes'
> > In my case I would like to collate the result of all sub-processes in the
> > main process. So in the first approach (forEach) do you think I can add a
> > <receive /> after <invoke /> as shown below
> >
> > <bpel:forEach parallel='yes' ...>
> >         initialize the counter here
> >         <scope>
> >                <partnerlink .. /> access the EPR array using the index
> > counter and assign it to the partnerlink.
> >                <invoke .../>
> >                <receive .../> to receive the response from above invoke
> >          </scope>
> > </bpel:forEach>
> >
> >
> In BPEL a sub-process is implemented by using a <SCOPE /> within the
> <PROCESS />. Just to clarify your sub process definition is actually a full
> blown process. Am I right?
> Yes, you can add a <RECEIVE /> after <INVOKE />, make sure you use
> correlations. Also, any variables defined within the <SCOPE /> is a local
> variable and cannot be accessed outside of it.
>
> Example forEach Parallel:
> https://github.com/apache/ode/blob/master/bpel-scripts/src/
> main/resources/2.0/good/foreach/ForEach2-2.0.bpel
>
>
> > 2) While loop with async communication and explicit correlation
> > ‚ÄčIn case of while loop, the execution is sequential. This is ok for
> <invoke
> > /> activities. But may not work for <receive /> activities because there
> is
> > no guarantee that the responses will be received in the same order of
> > invoke.
> > Or putting <receive /> in <while> will create an implicit <flow>
like
> > <forEach> loop?
> >
> > Thank you once again.
> >
> > JK
> >
>
> There is no guarantee of order of message processing. But, if you can make
> a unique correlated value relate for every invoke-receive then you can know
> which receive relates to the invoke. So, it doesn't matter in which order
> the receive has arrived.
>
> <FOREACH> creates an implicit <FLOW> as per the bpel specification:
> http://docs.oasis-open.org/wsbpel/2.0/OS/wsbpel-v2.0-OS.html#_Toc164738521
> <WHILE> does not create any implicit <FLOW>.
>
> regards,
> sathwik
>

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