Re: [wsbpel] implicite links of the runtime engine (was: Implicit<sequence> macro)

[Assaf Arkin <arkin@intalio.com>]

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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