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Subject: Re: [wsbpel] Issue - 120 - What are the semantics when an initial<receive> has no correlation set?
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 >> WSBPEL TC pages >> <http://www.oasis-open.org/apps/org/workgroup/wsbpel> on a regular >> basis. The current edition, as a TC document, is the most recent >> document with the title in the "Issues" folder of the WSBPEL TC >> document list >> <http://www.oasis-open.org/apps/org/workgroup/wsbpel/documents.php> >> - the next posting will include this issue. The list editor's >> working copy, which will normally include an issue when it is >> announced, is available at this constant URL >> <http://www.choreology.com/external/WS_BPEL_issues_list.html>. >> >> >> 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 >> >> To comment on this issue, please follow-up to this announcement on >> the wsbpel@lists.oasis-open.org >> <mailto:wsbpel@lists.oasis-open.org> list (replying to this >> message should automatically send your message to that list), or >> ensure the subject line as you send it *starts* "Issue - 120 - >> [anything]" or is a reply to such a message. >> >> To add a new issue, see the issues procedures document (but the >> address for new issue submission is the sender of this announcement). >> >> To unsubscribe from this mailing list (and be removed from the >> roster of the OASIS TC), go to >> http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgroup.php. >> >> >
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