RE: [wsbpel] Issue 47 and WS-I BP 1.0

["Ugo Corda" <UCorda@SeeBeyond.com>]

Title: Message

Hi Tony,

 

It looks like one of your major concerns about using BP 1.0 is its alleged prohibition of using any WSDL bindings other than SOAP/HTTP. Please look at my previous notes for my elaboration on this subject.

 

Ugo

-----Original Message-----
From: Fletcher, Tony [mailto:Tony.Fletcher@choreology.com]
Sent: Friday, October 03, 2003 7:11 AM
To: Ugo Corda
Cc: BPEL OASIS
Subject: RE: [wsbpel] Issue 47 and WS-I BP 1.0

Dear Ugo and others,

 

First I have to say that the opinions expressed in this mail are my own individual opinions based on my current understanding (that is always amenable to update on the absorption of new information!).

 

Saying that a minimum of one portType must obey the WS-I Basic Profile is an interesting get out, but it raises other issues as Peter has shown and fudges the real issue - see below.

 

It seems that the application of the BP will not material affect the BPEL language itself except possibly in some details (but this could be significant - the devil is sometimes in the detail!).

 

However the BP, if applied strictly - which is its whole purpose - will effect BPEL driven communications.

 

My impression is that the prime motivation for BPEL is portability.  If the TC is going to adopt interoperability as a first rank goal, then I think we should recognise this and maybe even have a vote on whether this should be a prime goal.

 

BPEL demands the use of WSDL and if we then apply the BP then this not only constrains the WSDL but also demands the constrained use of SOAP,  HTTP, and XML.  For instance SOAP over SMTP is clearly non-conformant

(BP 1.0a R0001 --> R2401 (R2702)  --> R1141(R1140) R4004 R2800 & R2801

 

 

Let us take a step back for a moment.

 

It seems to me that if we do accept BPEL instance run time interoperability as a major goal (and as I have stated above I think that is an issue the TC should explicitly decide on) then there are two extreme ways to achieve this - and probably a spectrum of options in between.

 

At one extreme you specify just one way of doing something and everyone has to implement all that is specified in the complete stack.  Nothing is optional to implement and the meaning of everything is made as clear as possible (this is always good independent of the approach!).  Not everything has to be used on each instance of communication but this is the only kind of optionality permitted.  It must always be possible to initiate a communication and get an understandable response (which is why only one way is supported in this case SOAP over a particular HTTP style and SOAP over SMTP is not supported).  This is the approach taken by the WS-I BP.

Pro:  The approach has worked well in the past.  Con:  It limits flexibility in the cause of interoperability.

 

The other extreme is specify whatever might be reasonably implemented and used, and to let partners agree which particular set of options they will use for communication between them.  This is essentially the approach used for EDI (through Message Implementation Guidelines) and this approach has been brought up to date in ebXML with the concept and use of a CPA.  The CPA is an agreed format configuration file that a group of partners agree to apply to their systems when engaging in the specified business process(es).  It can be agreed manually or semi-automatically.  It fixes the options to be used for those instances of communications and different CPAs can be applied dynamically if required.

Pro:  Allows flexibility in specification and implementation.  Con:  Automation of this approach is relatively new and it would require the development of a CPP/A for web services (the existing ebXML one could be used as a basis if it was modularised so that unwanted modules could be omitted and new web service relevant ones introduced)

 

In between these two extreme there is an approach that specifies a basic communications stack that must always be implemented, which allows the dynamic negotiation of additional features on any instance of communication.

 

Variations on these major possibilities are clearly possible such as having 2 or 3 (or more, but a small number) of 'Basic Profiles' and a very simple pre- communication agreement mechanism (slim line CPA) to agree which to use.

 

I think this is the territory we have, perhaps somewhat unwittingly, strayed into with the raising of the application of the WS-I BP, or not.

 

Best Regards,

Tony                          

	Tony Fletcher Technical Advisor Choreology Ltd. 68, Lombard Street, London EC3V 9L J   UK
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-----Original Message-----
From: Ugo Corda [mailto:UCorda@SeeBeyond.com]
Sent: 01 October 2003 18:55
To: Satish Thatte; Prasad Yendluri
Cc: BPEL OASIS
Subject: RE: [wsbpel] Issue 47 and WS-I BP 1.0

I see a few separate issues/questions connected to the relationship of BP 1.0 and BPEL.

 

1- Would BP 1.0 be restricting BPEL to the point that some of BPEL's functionality would not be available?

 

I cannot think of any such restriction off the top of my head.

 

2- Would the fact that BP 1.0 only addresses the SOAP/HTTP binding imply that also BPEL should be limited to that type of binding?

 

I don't think that anybody would imply that.

 

3- Should a BPEL process be offered as a Web service that is BP 1.0 compliant?

 

My answer would be yes.

 

3- Would it be fair to limit BPEL use to interacting with BP 1.0 compliant Web services only?

 

My personal answer would be yes. But I am a member of WS-I, and I understand other people might have different answers.

 

 

Ugo