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

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

When did Peter ask for "at least one opaque marker"?  I must have missed
it .. 

Satish
 

-----Original Message-----
From: Danny van der Rijn [mailto:dannyv@tibco.com] 
Sent: Monday, October 11, 2004 4:38 PM
To: ygoland@bea.com
Cc: wsbpel@lists.oasis-open.org
Subject: Re: [wsbpel] Issue - 82 - Proposal for Vote

We're back to my objection of describing abstract processes in terms of
conformance.  You may not have intended to go there Yaron, and I
apologize in advance if this is the case. 

My understanding of the current set of proposals, is that the query
string would not affect conformance proofs at all, and therefore DOES
NOT BELONG in abstract processes.  What you described would therefore be
termed an incompletely specified process, and one which does not meet
the definition of abstract process.

My preference, which I have (perhaps ineptly) stated in various ways,
coincides more with Peter's proposition that an abstract process is one
with at least one "opaque" marker, for whatever value of opaque marker
we decide upon.  Note that this has nothing to do with observable
conformance, just with degree of specificity. 

I would also argue that an abstract process is defined by intent, and
not by syntax, e.g. an abstract process is one that is marked
abstract=true.

I hesitate to go through my complete (but inept) arguments again, but
since it's been a while...

It makes more sense to me that there will be multiple conflicting
definitions of abstract process:  the observable conformance flavor, the
proper superset which you describe, others.  If we are going to preserve
a notion of an abstract process that has any meaning to a large number
of the audience of our specification, one way to do it would be to mark
the process with a string (perhaps a URI) that selects some
syntax/semantics/intentions of abstractness.  I worry that standardizing
that portion of "abstractness" that aids only in defining observable
conformance will increase the size and complexity of the BPEL spec
without giving benefit to a large portion of the community.  Therefore
I, for one, can not support the current proposals.  I would prefer the
absence of abstract processes to the current situation.

One counter-argument is that while the use-case you provide is
ill-specified, the observable conformance use case can be nailed down
precisely.  Using this as an argument for actually doing so, however,
and ignoring everything else, is specious.

Yaron Y. Goland wrote:

> 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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