RE: [sca-bpel] [Issue 53] BPEL Process: References withMultiplicity 0..1 - how are they supposed to work?

Proposal:

 

Change the sentences in section 2.1.1 which currently reads:

 

3.   
Stub Reference. [SBPEL2012] If neither [SBPEL2010]
nor [SBPEL2011] apply and the analysis of the process
determines that the first use of the partner link by any activity is in an <assign> activity that sets the partner role, then the
multiplicity MUST be "0..1" and the attribute wiredByImpl MUST be set to "true". 

to instead read:

 

3.   
Stub Reference. [SBPEL2012]
If [SBPEL2010] does not apply and the partner link has initializePartnerRole="no",
then the multiplicity MUST be "0..1" and the attribute
wiredByImpl MUST be set to "true". 

 

Note that (4), which follows this,
will turn any other partnerLink into a reference with multiplicity of 0..1 (not
wiredByImpl).

 

Michael

 

-----Original Message-----

From: Anish Karmarkar [mailto:] 

Sent: Thursday, August 06, 2009 3:39 PM

To: OASIS BPEL

Subject: [sca-bpel] [Issue 53] BPEL Process: References with Multiplicity 0..1
- how are they supposed to work?

 

This is now issue 53

http://osoa.org/jira/browse/BPEL-53

 

Mike Edwards wrote:

> 

>
Raiser:               
Mike Edwards

> 

>
Target:               

> 

> Description:

> 

>  

> Multi-valued references (ie 0..n and 1..n) are
discussed in the 

> specification at some length, particularly in
section

> 3.2.  Unfortunately, the case of 0..1
references is mentioned only in 

> passing, although it has some significant

> matters that need discussion and clarification.

> 

> Section 2.1.1 makes it clear that 0..1 multiplicity
references do exist 

> for BPEL processes.

> 

> Basically, it states that where a partnerLink is
determined to be a 

> reference, it will be 0..1 if
@initializePartnerRole="no"

> OR @initializePartnerRole is omitted.  It must
also be the case that the 

> partnerLink must not have its "first use"
as the

> target of an <assign/> operation.

> 

> Now, reading the BPEL 2.0 specification:

> 

>   
@initializePartnerRole="no" means that the BPEL Processor MUST NOT 

> initialize the partnerLink variable.

> 

>    @initializePartnerRole omitted
means that the BPEL Processor MAY 

> initialize the partnerLink variable.

> 

> 

> Now, the problems are these:

> 

> A)  If the partnerLink is NOT initialized, then
it is essential that it 

> is initialized by the BPEL process itself, since any

> attempt to use that partnerLink variable will
otherwise result in a fault.

> 

> So, if the partnerLink is marked
@initializePartnerRole="no", the 

> partnerLink must be supplied with a value - but

> how is such a value supplied to the BPEL process by
SCA?  The SCA BPEL 

> spec talks about the way in which

> serviceReferences are supplied in a variable typed
as a 

> serviceReferenceList for multi-valued references.

> There is no such equivalent for 0..1 references.

> 

> Even if the partnerLink is not marked with
@initializePartnerRole at 

> all, it is STILL possible for the partnerLink to

> be uninitialized and so unusable without being
assigned a value by the 

> BPEL process - this is the result of that

> "MAY" in the BPEL 2.0 spec, listed
above.  Again, there is no means by 

> which the BPEL process can get a

> serviceReference to assign into the partnerLink.

> 

> 

> B) If the partnerLink IS initialized, how can the
BPEL process determine 

> the difference between the case where the

> reference is wired and the case where the reference
is unwired?

> 

> There is no standard means for doing this in BPEL.

> 

> So, I think we may have a problem with 0..1
references in the SCA BPEL 

> spec.

> 

> Proposal:

> 

> None

> 

> 

> Yours,  Mike.

> 

> Strategist - Emerging Technologies, SCA & SDO.

> Co Chair OASIS SCA Assembly TC.

> IBM Hursley Park, Mail Point 146, Winchester, SO21
2JN, Great Britain.

> Phone & FAX: +44-1962-818014   
Mobile: +44-7802-467431  

> Email:  

> 

> 

>
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> IBM United Kingdom Limited - Registered in England
and Wales with number 

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Portsmouth, Hampshire PO6 3AU/

> 

> 

> 

> 

> 

> 

 

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