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Subject: RE: [wsbpel] implicite links of the runtime engine (was: Implicit <sequence> macro)
I believe a <sequence> activity can be replaced with a <flow
suppressJoinFailure="false"> activity with a few more caveats, to
produce equivalent control sequencing behavior. Why do you ask?
Satish
-----Original Message-----
From: Assaf Arkin [mailto:arkin@intalio.com]
Sent: Monday, June 16, 2003 1:48 PM
To: Satish Thatte
Cc: Eckenfels. Bernd; wsbpel@lists.oasis-open.org
Subject: Re: [wsbpel] implicite links of the runtime engine (was:
Implicit <sequence> macro)
Satish Thatte wrote:
>Assaf,
>
>Not sure what you are unclear on. As the comments before the flow
>version of the sequence say: "Finally, assume that the preceding flow
is
>slightly rewritten by linking A, B, and C through links (with
transition
>conditions with constant truth-value of "true") instead of putting them
>into a sequence". If you look at the second version, those links are
>indeed added.
>
Key word, actually two of them, being "slightly rewritten".
What if a <sequence> was properly rewritten as a <flow>? My question
again, is there a proper way to rewrite a sequence as a flow so you
preserve the semantics of the execution but only use the flow activity?
If so, what are the pros/cons of doing that?
arkin
>
>Let me know if I missed your point.
>
>Satish
>
>
>
>-----Original Message-----
>From: Assaf Arkin [mailto:arkin@intalio.com]
>Sent: Friday, June 13, 2003 10:08 AM
>To: Satish Thatte
>Cc: Eckenfels. Bernd; wsbpel@lists.oasis-open.org
>Subject: Re: [wsbpel] implicite links of the runtime engine (was:
>Implicit <sequence> macro)
>
>Satish Thatte wrote:
>
>
>
>>Sequences and sequentially linked activities in a flow are not
>>
>>
>identical. Please look at 12.5.4 for an example.
>
>
>>
>>
>>
>>
>I'm going to need a bit more explanation.
>
>The first example uses a <sequence> and the second one replaces that
>with a <flow>. In doing so it changes the behavior of the process. I
>understood that it does so intentionally to explain the usage of
<flow>.
>
>Suppose that it intended to preserve the semantics, and so included a
>join condition for activity B of the form ''getLinkStatus('X') or
>getLinkStatus('Y')'. In that case, how would the behavior differ
between
>
>the sequence and the flow?
>
>arkin
>
>
>
>> -----Original Message-----
>> From: Assaf Arkin [mailto:arkin@intalio.com]
>> Sent: Thu 6/12/2003 1:43 PM
>> To: Eckenfels. Bernd
>> Cc: wsbpel@lists.oasis-open.org
>> Subject: Re: [wsbpel] implicite links of the runtime engine
>>
>>
>(was: Implicit <sequence> macro)
>
>
>>
>>
>>
>> Eckenfels. Bernd wrote:
>>
>> >Hello,
>> >
>> >while implementing the BPEL4WS specification, I noted a few
>>
>>
>simplifications, which can be added to the runtime mode:
>
>
>> >
>> >- implicite flow-start links
>> > If the BPEL4WS parser adds links from a flow parent, to all
>>
>>
>the unlinked activities within, then the process engine does not have
>to search all activateable activities, but can just follow the links
>
>
>> >
>> >
>> I don't see why this would be a simplification. You would have
>>
>>
>to
>
>
>> determine all the unlinked activities and add an XML element to
>>
>>
>link
>
>
>> them to the flow, so essentially you're adding redundant
>>
>>
>information. If
>
>
>> we added that stuff my issue would then be "it's redundant
>>
>>
>information,
>
>
>> can't we just take it away?"
>>
>> >- implicite sequence links
>> > Instead of a sequence, the engine can simply use a flow,
>>
>>
>where all sequenced activities are linked together, that way the engine
>has not to implement two different scope styles
>
>
>> >
>> >
>> Here I would agree. If the semantics are identical then sequence
>>
>>
>becomes
>
>
>> a shortcut for a flow.
>>
>> arkin
>>
>> >I notice, that this is not so important for the spec, but
>>
>>
>especially the second case shows, that there is no need for the
sequence
>activity from a control flow point of few. I guess it would be good to
>add some comments on this in the spec. Or do i have missed a sematical
>difference between a sequence and a flow with linked activities?
>
>
>> >
>> >Greetings
>> >Bernd
>> >
>>
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>>
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>
>> >
>> >
>>
>>
>>
>>
>>
>>
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>
>
>
>
>
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"Those who can, do; those who can't, make screenshots"
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