Re: [wsbpel] Issue - 2 - Reopen the discussion

["Yaron Y. Goland" <ygoland@bea.com>]

Please see below

Trickovic, Ivana wrote:

> Sub-processes do not share variables from the scope it is "invoked" by, 
> but from scopes where it is defined. As I responded to Frank: For 
> example, a sub-process defined as a top-level process "shares" no 
> variables, because it is a top-level process and there is no parent 
> process. A sub-process defined directly under a process element "sees" 
> only process variables but not those defined within local scopes. 
> 

process
    variables
       variable name="foo"...
    subprocess name="bar"

So can subprocess bar see variable foo?

> Sharing data "by reference" introduces additional complexity (especially 
> when a sub-process is defined as a top-level process), because we have 
> to ensure consistent access to shared (transient) data.

Indeed but given the size of the messages that routinely get moved 
around by web services a by reference capability is not an option, it is 
a requirement.

> I would distinguish between sub-processes and functions. The problem is 
> that sub-processes may be complex, and may include interactions with 
> other partners, may take longer time. Sub-processes you mentioned are 
> rather functions doing probably simple computations (e.g. data 
> manipulation). I believe we should separate functions/sub-functions from 
> sub-processes.
> 

If someone is just doing calculations and such why would they use BPEL 
which is uniquely awful at calculations? I only see a function facility 
in BPEL being useful if it can handle long running processes. But I 
still believe that the calls should always be synchronous. If they are 
asynchronous then the function should be a stand alone web service. The 
idea here is that functions/sub-processes/etc., are a way to have 
portable bits of BPEL code. It is a substitute for having to type the 
code in directly. Just like all BPEL activities are synchronous (e.g. 
you call them and nothing happens on the thread until they return) so 
should calls to sub-processes.

> Regards,
> 
> Ivana
> 
>  > Can you provide an example of a programming language that
>  > doesn't allow
>  > subfunctions to be used in expressions? It would be
>  > interesting to see
>  > how they handled the situation of conditional logic re-usability.
>  >
>  > In any case, I object to this requirement and instead propose a
>  > requirement that sub-processes MUST be capable of returning a
>  > value that
>  > can be used in XPATH expressions/conditions/etc.
>  >
>  > I would also add a requirement around exactly what kind of data we
>  > expect to be able to pass into and out of sub-processes. For
>  > example, we
>  > probably will at least need to be able to pass through variables,
>  > partnerLinks and correlation sets. Probably an in/out type
>  > system would
>  > be best as it would also give us a very natural way to
>  > address the need
>  > to make calls by reference.
>  >
>  > > It would be worth agreeing on the above-mentioned set of
>  > requirements
>  > > first.
>  > >
>  > > Regards,
>  > >
>  > > Ivana
>  > >
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>  > > the OASIS TC), go to
>  > >
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> 
>  >
>  >
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