Re: [wsbpel] Link semantics and control dependencies

[<andrew.francis@mail.mcgill.ca>]

Hello:

> I believe that the following two fragments of the spec.
> contradict each other and I would like to gather second
> opinions about it:

Most of your arguments revolve around using links
that cross into a switch statement. My gut feeling
is that this is an ambiguous construct and probably
should be outlawed in WS-BPEL, or at least frowned
upon.

Like a previous post, and if I understand the example,
I will argue that the switch can be replaced with its all
link equivalent.I do this in order to illustrate how I think
DPE comes into play.
SW (T1 ->) A2, SW (T2 ->) A3

-> link (we don't care about its name)
T1 and T2 are transitionConditions

and for completeness A2 -> Dummy A3 -> Dummy
Dummy joinCondition("True")

In this scenario, if T2 evaluates to True (and T1
evaluates to False), A3 still cannot start because
A1 is not finished.

When A1 *finishes*, A3 can evaluate all of its links
and start.

Your mistake is:

"the status of link x2 is then set to negative since
branch A3 was not taken."

You forget that A3 cannot start executing until A1
is complete and link x1 is evaluated.

When A3 is finished and sets a value on link
X2, A4 can start. Note the logical order is correct,
A1 finished before A3, and A3 finished before A4. There
are no contradictions.

Marlon, the main thing I get out of your example is
that the specification is not clear on how switch
operates. I guess the correct behaviour of switch and
sequence in these circumstances by converting them into
their all link equivalents and working from there. That
said, I find the DPE algorithm elegant.

Cheers,
Andrew