RE: [wsbpel] Issue - 82 - Proposal for Vote

["Martin Chapman" <martin.chapman@oracle.com>]

During the Abstract BPEL Sub group meetings I noted that what might be
excluded to support one 
use case might not be excluded for another, and that defining that
single dividing line that makes sense to all use cases might take us for
ever to define and not really result in much!

Martin.

>-----Original Message-----
>From: Yaron Y. Goland [mailto:ygoland@bea.com] 
>Sent: 11 October 2004 23:59
>To: rkhalaf@watson.ibm.com
>Cc: wsbpel@lists.oasis-open.org
>Subject: Re: [wsbpel] Issue - 82 - Proposal for Vote
>
>
>I like the general direction the text is going in but there is one 
>particular issue that still worries me - why are abstract 
>processes not 
>a proper superset in functionality of executable processes?
>
>Imagine a company is using an abstract process as a template. Part of 
>the template is fully defined to provide a complete description of a 
>particular operation but the rest of the process is defined with less 
>detail. For the detailed section it is necessary to use a query string 
>on a from to indicate exactly which part of a source variable 
>should be 
>assigned to a destination.
>
>Currently the previous use case is impossible in BPEL because query 
>strings on from-specs are reserved for executable processes. Therefore 
>abstract processes do not have the same expressive power as executable 
>processes.
>
>For issue 82 to be resolved it is necessary for abstract 
>processes to be 
>well enough defined that it becomes obvious why limitations 
>such as the 
>query string restriction are necessary to meet the goals of abstract 
>processes. Yet no such description is provided below. Could you please 
>clarify this issue?
>
>	Thanks,
>
>		Yaron
>
>rkhalaf wrote:
>> 
>> 
>> In this proposal, we clarify abstract processes as requested 
>by Issue 
>> 82. The spec should reflect these clarifications to abstract 
>processes 
>> throughout its text.
>> 
>> --------
>> 
>> A BPEL abstract process defines the publicly visible behavior of the 
>> services it offers (all "myRole" in its partnerLinks), of course 
>> including its interactions along its partnerLinks with other 
>services. 
>> Abstract processes serve a descriptive role. They can be viewed as 
>> partially specified processes that are typically not intended to be 
>> executed. They are partially specified in that they are capable of 
>> abstracting away operational details. An abstract BPEL 
>process must be 
>> declared abstract by setting the abstractProcess attribute to “yes”. 
>> Operational details may be abstracted away either through 
>the omission 
>> of specific BPEL elements or attributes listed in the specification, 
>> or through the use of opaque tokens. Aside from these factors, they 
>> are well-formed process following the structure and restrictions in 
>> the specification regarding the process definition and the 
>constructs 
>> used.
>> 
>> Semantics of Abstract Processes:
>> 
>> A.       Although it might contain complete information that would 
>> render it
>> executable if the abstractProcess=”yes” attribute were 
>changed to “no” 
>> for executable BPEL, its abstract status states that any concrete 
>> realizations of it may perform additional processing steps that are 
>> not relevant to the audience to which it has been given.
>> 
>> B.      Abstract processes permit the use of nearly all of the 
>> constructs of
>> executable processes.  Thus there is no fundamental expressive power 
>> distinction between abstract and executable processes.
>> 
>> C.      An abstract process may omit certain details that 
>are mandatory for
>> BPEL executable processes. However, the semantics of the constructs 
>> used in such a process is exactly the same as their semantics in the 
>> executable context. An abstract process must comply with the syntax 
>> and semantics of the specification.  The syntactic elements that can 
>> be omitted in abstract processes where this would not be 
>permitted in 
>> executable processes are currently:
>> -       Those listed in the “extensions for executable processes” 
>> section of
>> the specification.
>> -       inputVariable/outputVariable/variable on invoke, receive, 
>> onMessage,
>> and reply.
>> -       An initiating receive activity (pending resolution 
>of issue 99).
>> 
>> D.      Abstract processes may include special syntactic extensions 
>> (“opaque”
>> entities of various kinds) that should be replaced with concrete 
>> entities  in any executable artifact that complies with an abstract 
>> process using such opaque entities. Which opaque entities are 
>> permitted is the scope of issue 107.
>> 
>> E. Abstract processes say nothing about *how* concrete, executable 
>> realizations of them should be implemented (ie: language, platform, 
>> etc) . (analogy to WSDL).
>> 
>> F. Multiple abstract processes together may be created to define a 
>> global view of a multi-party business protocol. However, the way in 
>> which they may be wired together (connecting partnerLinks a la WSFL 
>> global models) is out of scope of BPEL itself.
>> 
>> 
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> 
> 

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