Re: [wsbpel] Issue - 120 - What are the semantics when an initial<receive> has no correlation set?

[Danny van der Rijn <dannyv@tibco.com>]

yet according to issue 118, from which this issue sprang, it is illegal 
to have a receive that doesn't have a correlation set.

Yaron Y. Goland wrote:

> It occurs to me that we can break this problem down a little more.
>
> One can trivially imagine a web service that consists of exactly one 
> request/response pair that receives a message, processes it, sends a 
> response and exits. Such a webservice would have no need to use 
> correlation sets. Therefore I think we can be sure that at a minimum 
> we want to make it possible to define a BPEL that has a single start 
> activity with no correlation set that doesn't create a singleton.
>
> What this argues to me is that the default interpretation of a BPEL 
> with a start activity with no correlation set is that it is not a 
> singleton.
>
> Therefore what 120 really should be about is - do we want to 
> intentionally add an attribute or other mechanism to specify that a 
> BPEL process is intended to be a singleton?
>
> We already know we can simulate a singleton in BPEL by having an 
> instance with a start activity that is only known to the deployment 
> environment and then having all subsequent messages sent to the single 
> BPEL instance. But I readily admit that this is a less than clean 
> solution. It is best when possible to directly express one's semantics.
>
> So I think we can then rephrase the issue once again to - Is it worth 
> defining explicit singleton behavior in BPEL 2.0 (or whatever we call 
> it)?
>
> To which, given our other priorities, I think the answer is no. But I 
> realize that my answer is just a matter of opinion.
>
>     Just my two cents,
>
>         Yaron
>
> Ugo Corda wrote:
>
>>
>> I think the term "semantics" was used here primarily to refer to the 
>> expected behavior in case a second message is sent to the same 
>> <receive> at the time an instance is already active (see Issue 118 
>> discussions). Should the second message be understood as creating a 
>> new instance, or should it be seen as a message sent to a singleton 
>> instance (and therefore dropped since the corresponding <receive> is 
>> not active at that time)? As I remember from the issue 118 
>> discussions, use cases can be made for both interpretations.
>>  
>> Ugo
>>
>>     -----Original Message-----
>>     *From:* Ron Ten-Hove [mailto:Ronald.Ten-Hove@Sun.COM]
>>     *Sent:* Thursday, August 12, 2004 11:16 AM
>>     *To:* wsbpel@lists.oasis-open.org
>>     *Subject:* Re: [wsbpel] Issue - 120 - What are the semantics when an
>>     initial <receive> has no correlation set?
>>
>>     It seems to me that we can't actually read too much into the fact
>>     that an initiating <receive> activity doesn't initiate a correlation
>>     set at the same time. Two possibilities come to mind:
>>
>>         * The process is actually very simple, and doesn't need
>>           correlation (ie, it has no other <receive> activities).
>>         * The process initiates the correlation set in a later <invoke>
>>           activity.
>>     So it seems that it would be inappropriate to infer any special
>>     semantics to the <receive> in question.
>>
>>     -Ron
>>
>>     ws-bpel issues list editor wrote:
>>
>>>     This issue has been added to the wsbpel issue list. The issues
>>>     list is posted as a Technical Committee document to the OASIS
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>>>
>>>
>>>         Issue - 120 - What are the semantics when an initial <receive>
>>>         has no correlation set?
>>>
>>>     *Status:* open
>>>     *Categories:* Correlation <#category_correlation>
>>>     *Date added:* 19 Apr 2004
>>>     *Submitter:* Danny van der Rijn <mailto:dannyv@tibco.com>
>>>     *Date submitted:* 19 April 2004
>>>     *Description:* when an initial <receive> has no correlation set
>>>     should the instance be singleton, or be allowed to have multiple
>>>     instances outstanding in parallel?
>>>     *Changes:* 19 Apr 2004 - new issue
>>>
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>>
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