RE: [ebxml-iic] Use Case #2 Termination Cases (Nesting)

[Jacques Durand <JDurand@us.fujitsu.com>]

Title: RE: [ebxml-iic] Use Case #2 Termination Cases (Nesting)

inline <JD>

-----Original Message-----
From: Monica J. Martin [mailto:Monica.Martin@sun.com]
Sent: Friday, August 27, 2004 4:17 PM
To: Jacques Durand
Cc: 'Michael Kass'; ebXML IIC - main list (E-mail) (E-mail);
tsakach@certivo.net; phogan@sinotechnologies.com; Dale Moberg
Subject: Re: [ebxml-iic] Use Case #2 Termination Cases (Nesting)

>         24 August 2004:
>
>             [MIKE2] - Additionally, I would suggest (just to keep the
>             rules as simple as possible) that <AbortThread> be
>             permitted for "serial" Threads as well. I do not see any
>             reason why/how this would have a negative effect on
>             execution flow. Basically, this would say that an
>             "aborted" serial Thread simply exits ( for whatever
>             <TestAssertion> result in that Thread) and workflow
>             continues wiht the next instruction after that Thread.
>             This can be thought of as the serial version of the
>             "dangling concurrent thread", whose result is not
>             consequential to the ultimate result of the Test Case.
>             This keeps the rules simple for all Threads.
>
>             Comments?
>
>             [Jacques Durand] Everything above and before is OK to me,
>             with some reserve on the notion of "serial" thread. I
>             assume "serialization of threads" has the following
>             semantics (since I assume that splitting/joining are the
>             only way to combine threads here):
>
mm1: In workflow (process), you may have several concurrent threads that
when one becomes active, the others are disabled. It seems this still
follows your logic, Mike, I believe.

<JD> I believe Mike has more in mind the fact that threads could just be chained
one after the other (no concurrency assumed like in the "exclusive-or" fork of BPSS)
so I suspect just a convenience feature from Mike... (right Mike?), as threads others
than the "root" or main, must always be forked (split), so "serial" just means some
implicit way to split them (that I previously described).

>             (2) if for some reason you want the thread to jump
>             directly to "successful completion" if TestAssertion =
>             True/False, then we need a 4th action besides "continue",
>             "abort", "exit[testcase]": we could call it "endthread".
>             In that case that is just one more way to terminate
>             positively a thread (so join semantics is same as for
>             normal completion)
>
mm1: This follows what we discussed as endsWhen, re: ends when
'endthread.' However, I'll have to think a bit more about the Main
thread and containing threads because of this in the previous v1.1 ebXML
BPSS (I've cc: Dale Moberg so he can comment as well):

<JD> the main thread can be implicit, as Mike suggests (but then the container of
the test case script still has thread semantics) again a convenience feature.</JD>

"The Success and Failure elements represent an aggregation of a state
and a transition to this particular state. This transition like regular
transitions can be guarded by a conditionGuard. The conditionGuard can
be used to indicate that a binary collaboration ends in success or
failure based on the fact that the last business transaction activity
response is a business document of a particular type, or based on the
content of the response. It is important to note that the success or
failure of the collaboration does not affect the success or failure of
the individual business transaction activities, which compose the binary
collaboration. In particular, the nature of the commitments is not
changed when the collaboration ends in a specific state. The success or
failure of a collaboration is rather an indication, which can be
reported on, or acted upon to initiate other collaborations. If several
completion states are specified within a collaboration definition, the
business collaboration run-time instance state is “complete” as soon as
one of the completion state is reached. It is the responsibility of the
designer to ensure that all completion states are mutually exclusive and
that once one of them is reached there are no further Business Activity
open. A timeout exception will be generated by the BSI in such a case."

<JD> Using variables, our script can verify mutual exclusive threads execution:
i.e. as soon as a thread is "elected", it sets a variable, say mutex="true".
Each mutually exclusive thread tests this var in a TestAssertion somewhere at their beginning,
and exit on failure if mutex="true" at the time it does the verification.

>         - when threads are joined, an aborted thread will
>         automatically cause failure of an and-join (which aborts the
>         container thread) [MIKE2] - My question is, why abort the
>         container Thread as well? If a Join simply allows/disallows
>         (gates) workflow continuation based upon the result of the
>         Join, then it appears that in either case (whether Join
>         condition is satisfied or not), there is no reason to "abort"
>         the parent Thread. There is no "error" (that I can see) either
>         way with the Join that would require an "abort" of the parent
>         Thread. If the and/or Join result allows continuation of
>         workflow , then the parent Thread would simply finish its
>         workflow execution, and return control to IT's parent Thread
>         (ther parent's parent).
>
mm1: Only as long as one contained thread completed successfully correct?

<JD> at the bottom of this, we have to decide whether:
(1) a thread can have three states only: not started, in execution (including hanging),
and complete.
(2) a thread can have one more state: aborted. If that's the case, we need
to escalate the semantics of a thread "aborting" ,for the container thread,
and I'd suggest that it depends on the way the thread is split and joined.
This "abort" is a little like an exception.
Now, my main priority at this point, is ease of implementation, and avoid
unnecessary complexity - and delay. So if we feel time is a little short to do (2) properly, I'd rather skip the "abort" for now - remember that there is room for other releases.

We may also choose to just introduce a simpler operator to complete the thread, instead
(like jumping to its end).

>         If the and/or Join result precludes workflow continuation...
>         fine... The logic rules have been followed, and again, control
>         is returned to the "parent's parent Thread". No abort is
>         necessary. The only scenario that I can see that would require
>         the parent Thread to "abort" is if a <TestAssertion> operation
>         run IN THAT Parent Thread implicilty or (as I would prefer)
>         explicitly sets an <AbortThread> instruction based upon the
>         result of that <TestAssertion>.
>
>             [MIKE] - There are a couple of issues here: The only way a
>             "Main" Thread could abort (based on your suggested logic
>             for concurrent Threads) is if it is concurrently run (i.e.
>             the Main Thread is <Split>). But if it is the Main thread,
>             why would you <Split> it?
>
mm1: We did have a case on start that there was a split in the previous
specification (fork).

<JD> there is always a "top" thread, whether it is called "main" or not. Every other thread
is "split" from there (or from previously split thread).

>             [MIKE2] - I would like to suggest setting the final state
>             of the Test Case to "undetermined" if a child (of the
>             <TestCase>) <TestAssertion> encounters an <AbortThread>
>             instruction during its workflow. Otherwise, all other
>             <Thread>s simply "abort" and pass control back to their
>             parent Thread. If execution proceeds to logical conclusion
>             without an exception conditions or explicit exits, then
>             the Test Case final result is "pass".
>
<JD> again - if we introduce abort - I would not give test case termination semantics
to occurrences of abort: I woudl only give it "flow" semantics (i.e. affecting
the way the tset case executes, somewhat similarly as an exception).
So only when the top (main) thread is itself aborting (either from one of its
TestAssertion, or from and-joining an aborted child thread), then I would worry about
the meaning for termination, and favor "undetermined" here.
So it appears we might need more time to reach a consensus on "abort" and I would not
have problem postponing this to a future release.

Jacques

mm1: I've referenced the original section for Dale's benefit for comment
(if he has time). Thanks.
Reference:
http://www.oasis-open.org/archives/ebxml-iic/200408/msg00023.html (at
least the start of a long trail of comments)

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