RE: [wsbpel-abstract] Potential requirements and use case

["Satish Thatte" <satisht@microsoft.com>]

I think we are agreeing on a few things

1. abstract BPEL allows partial specification of executable processes.

2. we need a precise definition of conformance between a partial process and any executable process that claims to be its completion

3. We do not want to preclude any use case for abstract processes, including 

a. A notation for specifying the externally visible behavior of a web service or a collection of web services where the notation may be used with various degrees of austerity as appropriate for the needs of the specifier,

b. A notation for exchange of process requirements across autonomous entities where the abstract and the executable process are NOT "owned" by the same entity, and

c. A notation for partial specification in a modeling context where the abstract and the executable process ARE "owned" by the same entity.

4.  <opaque> activities and expressions are primarily intended as a proposal for allowing the designer of an abstract process to express his/her intentions regarding mandatory points of extension.  The purpose of <opaque> is NOT to specify all allowable points of extension, prohibiting all other potential points of extension in the completion of an abstract process.  Secondarily, <opaque> activities and expressions serve as a convenience for technical specification and validation using a single schema.

I would argue that the technical convenience argument for <opaque> is a weak one because the syntactically mandated completion points can be easily found by tools and forcing an abstract process designer to explicitly design them in helps tools and BPEL specification writers at the expense of the users of abstract BPEL, i.e., those who read and write instances of abstract BPEL.  This is especially the case for use case (a) above where brevity and readability are likely to be very important.

I believe the primary intention of the <opaque> proposal as a mechanism for expressing the intention for mandatory extension applies primarily to use case (c) and as such I would argue that it belongs more in the realm of a tools oriented extension rather than an essential aspect of abstract BPEL.  

Satish


________________________________________
From: Satish Thatte 
Sent: Thursday, July 15, 2004 10:20 PM
To: wsbpel-abstract@lists.oasis-open.org
Subject: RE: [wsbpel-abstract] Potential requirements and use case

I would add that in real scenarios external views are often linked with modeling requirements.  A large company may specify a "required external view" in the form of an abstract process for its partners' processes without dictating how such a process is completed by the partners.  The partners may need to take their required external view and use it as input into a modeling environment for completion and implementation in their own environments.  However, it is extremely unlilely that the large company will dictate exactly how the process is to be completed by specifying the exact places where it must be extended.  Each partner may of course complete and implement the process differently, so long as all maintain the externally visible contract specified by the abstract process.
 
We would therefore be better off specifying the base techical notion of abstract processes as partial processes and we should avoid attempts to narrow the space of use cases artificially.
 
Satish

________________________________________
From: Satish Thatte [mailto:satisht@microsoft.com]
Sent: Thu 7/15/2004 9:41 PM
To: Ashwini Surpur; wsbpel-abstract@lists.oasis-open.org
Subject: RE: [wsbpel-abstract] Potential requirements and use case
Aren't you confusing a use case with a set of "requirements" marked with "MUST"?

I am not opposed to the use of abstract BPEL for supporting modeling tools, if it suits.

I am opposed to structuring abstract BPEL in such a way that it is ONLY or PRIMARILY focused on supporting modeling tools.

There are several reasons for this.

1.  This is inconsistent with the current spec which expresses the intentions of the original authors rather clearly, as well as the charter.  All of these emphasize the public view aspect of abstract BPEL and it is not at all clear that the use of OPAQUE is suitable for that.

2.  The *technical* motivation for this push away from the original intentions is not clear -- it would be helpful to have that explained.

3.  At a technical level, we recognize that abstract processes are partially specified executable processes.  One can provide an external view as a partially specified process by eliminating all unnecessary detail.  One can also use the very same partial specification as the basis for representing intermediate states in a modeling exercise. 

In both cases you need a notion of faithful completion.  I do not buy that faithful completion is a purely syntactic matter of specifying OPAQUE syntactic elements.  This may be adequate for some narrow use cases but is clearly suboptimal for the technology as a whole. 

It is not, and has never been our charter to specifically address the requirements of (visual or other) tools for process modeling.  I simply see no reason to bring that in as the canonical use case.

It is time we moved beyond this.  Let us use the call tomorrow to do so.

Satish



________________________________

From: Ashwini Surpur [mailto:Ashwini.Surpur@oracle.com]
Sent: Thu 7/15/2004 4:49 PM
To: wsbpel-abstract@lists.oasis-open.org
Subject: [wsbpel-abstract] Potential requirements and use case



Hi,

Here is a  use case and some requirements that we feel should be
satisfied. If needed, we can discuss this at tomorrow's conf call.

Thanks,
Ashwini