[ebxml-cppa-negot] RE: BPSS Start element

[Martin W Sachs <mwsachs@us.ibm.com>]

JJ,

Thanks for the reply.  However, I would like to restate my question.

One of the essential services a BSI can provide is to ensure that everyone
is obeying the choreography described in the BPSS instance. That is
especially important in a world in which two trading partners may have
obtained their application software from different vendors. In order to
perform this service, the BSI must know what is the start of the
choreography.

I have a BPSS instance two binary collaborations, one nested inside the
other, and both have Start elements. How does a BSI know which Start
element actually starts the choreography?

Regards,
Marty

*************************************************************************************

Martin W. Sachs
IBM T. J. Watson Research Center
P. O. B. 704
Yorktown Hts, NY 10598
914-784-7287;  IBM tie line 863-7287
Notes address:  Martin W Sachs/Watson/IBM
Internet address:  mwsachs @ us.ibm.com
*************************************************************************************


                                                                                                                                        
                      "Jean-Jacques                                                                                                     
                      Dubray"                  To:       Martin W Sachs/Watson/IBM@IBMUS, <ebtwg-bps@lists.ebtwg.org>, <ebxml-cppa-     
                      <jjd@eigner.com>          negot@lists.oasis-open.org>                                                             
                                               cc:                                                                                      
                      08/09/2002 09:31         Subject:  RE: BPSS Start element                                                         
                      AM                                                                                                                
                                                                                                                                        
                                                                                                                                        



Marty:
>>
>>1. How does a BSI know the starting point of a choreography defined in
a
>>BPSS instance document?  Is that the function of the Start element?
If
>>not, what is the indicator? (It can't be preCondition since in BPS
1.05,
>>that attribute is for documentation only.)
>>
[JJ] The start element is used to "point to" the first business
transaction activity of the binary collaboration (actually nothing
prevents you to point to a fork element therefore enabling several BTA
at the same time). The request of the BTA pointed to by the start
element is the message that will initiate the binary collaboration


>>2. If a BPSS instance contains more than one binary collaboration (not
>>nested), are they treated as separate choreographies?  Should each
have a
>>Start element?
[JJ] Yes they are completely independent and all should have a start
element.
>>
>>3. If a BPSS instance contains one "top-level" binary collaboration
and
>>another binary collaboration nested inside it, should both binary
>>collaborations have start elements?  If so, how does a deployment tool
or
>>BSI know where the starting point is?  It seems to me that it would
have
>>to
>>analyze the flow in detail to figure out where the choreography
begins.
>>
[JJ] I don't see a probleme there, the start element is a pseudo-state,
so in the case they are nested (as a Collaboration Activity in the
parent binary collaboration definition), the BSI will simply expect the
next BTA will be the one pointed to by the start element of the child
collaboration. In other words the BSI does not "stop" at this start
element, it automatically transitions to the BTA pointed to by this
element. You always need a start element to point to where you start.
Otherwise, you would have to analyze all the transitions and detect the
BTA that does not have a transition to it.


>>I have a suspicion that the answers are:
>>
>>1. The Start element is supposed to tell the BSI where the
choreography
>>starts.
>>
>>2. Non-nested binary collaborations are separate choreographies and
each
>>needs a Start element.
>>
>>3. The nested binary collaboration should not have a Start element
since
>>the choregraphy starts with the top-level binary collaboration and a
>>Transition element defines the starting point of the nested binary
>>collaboration.
>>
>>Am I right?
>>
>>Incidentally, BPSS 1.05 states that for the Start element,
>>maxOccurs="unbounded" although the text in 8.1.24 strongly implies
that
>>maxOccurs should be "1".
>>
[JJ] That could be a bug, I'll look into it. Conceivably, it is not
impossible to think of multiple start element, the question is simply,
once such a collaboration has started to we disable the other start
element or do we leave them enabled? Note that this behavior can be
achieved with a single start followed by a fork (XOR or All) which will
be followed by the corresponding BTAs.

Cheers,

JJ-


>>Regards,
>>Marry
>>
>>**********************************************************************
****
>>***********
>>
>>Martin W. Sachs
>>IBM T. J. Watson Research Center
>>P. O. B. 704
>>Yorktown Hts, NY 10598
>>914-784-7287;  IBM tie line 863-7287
>>Notes address:  Martin W Sachs/Watson/IBM
>>Internet address:  mwsachs @ us.ibm.com
>>**********************************************************************
****
>>***********
>>
>>
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