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Subject: Re: [wsbpel] Issue 6 - Rough draft of proposal for vote
in that case, don't you have some serious concurrency issues?
Yaron Y. Goland wrote:
> Actually no. I just meant them as generic wrappers. I could just as
> easily have used sequence instead of scope.
>
> Danny van der Rijn wrote:
>
>>
>>
>> i assume that the leaf scopes are serializable and that's why they're
>> there?
>>
>> Yaron Y. Goland wrote:
>>
>> > Below is an example of 2 out of 3, it is generalizable from there.
>> >
>> > scope
>> > variables
>> > variable name="counter" type="xs:int"
>> > sequence
>> > assign
>> > copy
>> > from literal="true"
>> > "0"
>> > to
>> > $counter
>> > flow
>> > scope
>> > ...
>> > assign
>> > copy
>> > from
>> > $counter + 1
>> > to
>> > $counter
>> > switch
>> > case
>> > condition
>> > $counter >= 2
>> > break
>> > scope
>> > ...
>> > assign
>> > copy
>> > from
>> > $counter + 1
>> > to
>> > $counter
>> > switch
>> > case
>> > condition
>> > $counter >= 2
>> > break
>> > scope
>> > ...
>> > assign
>> > copy
>> > from
>> > $counter + 1
>> > to
>> > $counter
>> > switch
>> > case
>> > condition
>> > $counter >= 2
>> > break
>> >
>> >
>> > Trickovic, Ivana wrote:
>> >
>> >>
>> >>
>> >> Yaron,
>> >>
>> >> Would you illustrate how break activity could be used? How does it
>> >> resolve problems tackled by proposals we have on table at the
>> moment?
>> >>
>> >> Regards,
>> >>
>> >> Ivana
>> >>
>> >> > -----Original Message-----
>> >> > From: Yaron Y. Goland [mailto:ygoland@bea.com]
>> >> > Sent: Dienstag, 14. September 2004 00:01
>> >> > To: Alex Yiu
>> >> > Cc: Trickovic, Ivana; Axel Martens; Frank Leymann; Dieter
>> >> > Roller; Dieter
>> >> > Koenig1; edwink@collaxa.com; [email protected];
>> >> > wsbpel@lists.oasis-open.org
>> >> > Subject: Re: [wsbpel] Issue 6 - Rough draft of proposal for vote
>> >> >
>> >> >
>> >> > I believe that the complexity of the current proposal is well
>> >> > above the
>> >> > capabilities of what I expect to be the average BPEL programmer.
>> >> > Completion conditions, ignorable faults, new XPATH functions,
>> etc.
>> >> > introduces a lot of complexity that I believe that average BPEL
>> >> > programmer would not be interested in dealing with.
>> >> >
>> >> > We know from many decades of language experience that average
>> >> > programmers can deal with break/continue. I know from at
>> >> > least our own
>> >> > experience at BEA that users can deal with the concept of a
>> >> > flow where a
>> >> > break in the flow results in the other members of the flow being
>> >> > terminated in the BPEL meaning of the term.
>> >> >
>> >> > Defining a break activity and specifying that if break is used
>> in the
>> >> > context of flow then this means that the flow activity ends
>> and any
>> >> > uncompleted members of the flow are terminated would both fit
>> >> > directly
>> >> > into BPEL's existing syntax and semantics and I believe be
>> >> > simple enough
>> >> > that the average programmer can handle it. I would therefore
>> >> > offer break
>> >> > (and it's relative 'continue') as an alternative.
>> >> >
>> >> > Thanks,
>> >> >
>> >> > Yaron
>> >> >
>> >> > Alex Yiu wrote:
>> >> >
>> >> > >
>> >> > > Hi,
>> >> > >
>> >> > > Ivana, thanks for sending out this proposal.
>> >> > > I believe a number of us (including me) like the
>> >> > <completionConditon>
>> >> > > construct from your proposal high level speaking.
>> >> > >
>> >> > > After reading the proposal, I guess we need to work on a
>> number of
>> >> > > details. I would like to ask a few questions / mention a few
>> >> points:
>> >> > >
>> >> > > * Minor syntax and semantics questions :
>> >> > > o Do we want to allow expression for branch
>> >> > attribute? instead
>> >> > > of just a constant integer?
>> >> > > o We may need to some minor syntax adjustment for
>> >> > expression
>> >> > > attribute because we have passed Isseu 13 already.
>> >> > > o If answers to the above question are yes, then
>> >> > the condition
>> >> > > syntax may become a choice (xsd:choice) of the
>> >> > following two:
>> >> > > <condition
>> >> > > >
>> >> expressionLanguage="anyURI"?>boolean-expression</condition>
>> >> > > <branchCondition
>> >> > > >
>> >> expressionLanguage="anyURI"?>integer-expression</condition>
>> >> > >
>> >> > > * About completionConditionFailure : it looks like a
>> >> > nice idea so
>> >> > > far ...
>> >> > >
>> >> > > * About the new "isCompleted()" function : I am not
>> >> > against this
>> >> > > function. But, I tend to think there are usually BPEL
>> >> > variables
>> >> > > being modifed as the execution result of a flow
>> >> > activity. (See the
>> >> > > train-or-plane-and-hotel example). Is it more typical
>> to have
>> >> > > completionCondition to be evaluated on those variables?
>> >> > > Also, after the completion of the whole flow, it is
>> >> > not uncommon
>> >> > > for people to have logic to find out which branch is
>> finished
>> >> > > (especially when "or" is involved in the condition). The
>> >> > > "isComplete()" function would be available only within
>> the
>> >> > > completionCondition within the flow. People may get
>> >> > confused and
>> >> > > attempt to use the "isComplete()" function outside
>> >> > the flow. If
>> >> > > the completionCondition relies on variables, the same
>> >> logic is
>> >> > > applicable outside of the flow.
>> >> > >
>> >> > > * About the IgnoreFault semantics: I recall this
>> >> > ignoreFault idea
>> >> > > back to March F2F. With ignoreFault semantics, it
>> essentially
>> >> > > introduces two brand new semantics.
>> >> > > o It turns <flow> into a semi-<scope> like construct
>> >> > > o It adds this new "ignoreFault" semantics: which
>> catches
>> >> > > certain fault and the catching action will not
>> cause
>> >> any
>> >> > > scope to be marked as faulted.
>> >> > >
>> >> > > I tend to think this "ignoreFault" functionality has
>> >> > quite a heavy
>> >> > > weight impact to <flow> and fault handling picture in
>> >> > BPEL. If there
>> >> > > is an alternative way to achieve similar business
>> >> > logic, I would go
>> >> > > for the alternative way.
>> >> > >
>> >> > > Quoted from Ivana's email:
>> >> > > " Not all activities must complete in order the
>> enclosing flow
>> >> > > activity to complete. The way to identify that an
>> >> > enclosed activity
>> >> > > did not complete is to propagate faults. "
>> >> > >
>> >> > > I agree with the first sentence. But, I am not sure
>> >> > that propagating
>> >> > > fault is the only way to identify an enclosed activity
>> did not
>> >> > > complete. I would rather use a scope as an activity
>> enclosed by
>> >> > > flow. If we wish to suppress any minor fault which
>> >> > happens during
>> >> > > the execution of the scope, then we can just add a
>> >> > fault handler. If
>> >> > > the fault that happen, the scope will be marked as
>> "faulted".
>> >> > >
>> >> > > The completeConditon can identify the "incomplete" state
>> of the
>> >> > > scope by two ways:
>> >> > >
>> >> > > * completeCondition can be evaluated based on BPEL
>> >> > variables,
>> >> > > which are set to "incomplete" state by pre-flow
>> >> > initialization
>> >> > > or related fault-handler logic.
>> >> > > * branch-based condition will interprete a faulted
>> scope as
>> >> > > "incomplete" branch and will not count them into
>> >> > the required
>> >> > > N branches.
>> >> > >
>> >> > > This will allow us to suppress minor fault with or
>> without the
>> >> > > <completionCondition> construct. Please see the
>> >> > following example.
>> >> > > It is already legal and working today. It shows how to
>> suppress
>> >> > > "foo:barFault" without the <completeCondition> construct
>> >> > >
>> >> > > <flow>
>> >> > > <scope name="A">
>> >> > > <faultHandler>
>> >> > > <catch faultName="foo:barFault" ... > ... </catch>
>> >> > > </faultHandler>
>> >> > > <sequence>
>> >> > > ... <invoke name="doA" ... /> ...
>> >> > > </sequence>
>> >> > > </scope>
>> >> > > <scope name="B"> ... <!-- similar to A --> ... </scope>
>> >> > > </flow>
>> >> > >
>> >> > > If the invoke of "doA" triggers "foo:barFault", the
>> >> > scope "A" will
>> >> > > be marked as faulted. On the other hand, scope "B" will
>> >> > be allowed
>> >> > > to continue and complete. After scope "B" is completed, the
>> >> > > compensation handler of scope "B" will be installed.
>> And, the
>> >> > > overall execution of flow is still considered a normal
>> >> > completion.
>> >> > >
>> >> > > I hope I have illustrated we can achieve similar logic
>> without
>> >> > > introducing a new "ignoreFault" construct and concept to
>> BPEL.
>> >> > >
>> >> > > What "completionCondition" does should be just
>> >> > providing a way to
>> >> > > pro-actively cancel/terminate other flows without
>> >> > waiting to them to
>> >> > > complete or to be faulted.
>> >> > >
>> >> > > * About "Cancel-other-flows": (Let me consolidate what
>> I am
>> >> > > leaning towards so far.) We need to formal define the
>> >> > notion of a
>> >> > > " cancel-other-flows " mechanism. This mechanism is
>> >> > specified and
>> >> > > attached to <flow> construct (and future parallel forEach
>> >> > > construct). When this mechanism is triggered by one
>> >> > of parallel
>> >> > > flows, it will cancel/terminate other parallel flows
>> which
>> >> are
>> >> > > still running, after the triggering flow is completed.
>> If the
>> >> > > other flow activties are scope activities, the scope
>> will be
>> >> > > marked as cancelled.
>> >> > >
>> >> > > This mechanism will be triggered upon the
>> >> > completionCondition is
>> >> > > evaluated to be true.
>> >> > >
>> >> > > [Note: (a) since this mechanism is triggered by
>> >> > without using any
>> >> > > fault directly. This will again decrease the need of
>> >> > "ignoreFault"
>> >> > > construct (b) This mechanism will affect the wordings
>> >> > of Issue 135
>> >> > > to an extent.]
>> >> > >
>> >> > > [Question: again, should we enforce scope-only
>> activity when
>> >> > > completionCondition is used? I tend to say yes.]
>> >> > >
>> >> > >
>> >> > >
>> >> > > Thank you all for following and reading this email thread!!!
>> >> > >
>> >> > >
>> >> > >
>> >> > > Regards,
>> >> > > Alex Yiu
>> >> > > > >
>> >> > >
>> >> > > Trickovic, Ivana wrote:
>> >> > >
>> >> > >> > >>
>> >> > >> Here is a proposal for the completion condition - it
>> >> > addresses some
>> >> > >> issues not tackled so far (at least not in case of
>> >> > >> <completeCondition>). It is a version of the proposal for
>> >> > completion
>> >> > >> condition for the bundle element. This proposal includes
>> >> > comments from
>> >> > >> many people including Frank Leymann, Dieter Koenig, Dieter
>> >> > Roller and
>> >> > >> Satish Thatte. It does not mean that they completely
>> support the
>> >> > >> proposal - they may have issues with any part of the proposal.
>> >> > >>
>> >> > >> > >>
>> >> > >> > >>
>> >> > >> Completion condition
>> >> > >>
>> >> > >> =====================
>> >> > >>
>> >> > >> The current semantics of the flow activity is that it
>> >> > waits for all
>> >> > >> concurrent activities to complete. The completion also
>> >> > means that an
>> >> > >> enclosed activity/scope may end abnormally or be skipped
>> (e.g. the
>> >> > >> join condition of the activity evaluated to false). If a
>> fault is
>> >> > >> thrown within an enclosed activity/scope and one of the
>> >> > local fault
>> >> > >> handlers catch the fault (and does not rethrow the fault), the
>> >> > >> enclosed activity/scope will be deemed to be completed
>> >> > (although ended
>> >> > >> abnormally). If a fault is not caught by any local fault
>> >> > handler (or
>> >> > >> is rethrown) the flow activity will terminate all active
>> >> > concurrent
>> >> > >> activities and corresponding fault handler may be initiated.
>> >> > >>
>> >> > >> > >>
>> >> > >> A completion condition for the flow activity is needed for
>> >> > scenarios
>> >> > >> where not all concurrent activities of a flow activity
>> >> > must complete
>> >> > >> in order the flow activity to complete. Note: We are not
>> >> > talking about
>> >> > >> "successful completion" of enclosed concurrent activities
>> >> > because that
>> >> > >> would not be consistent with the semantics of the current
>> >> > flow activity.
>> >> > >>
>> >> > >> > >>
>> >> > >> The completion condition may have different flavors, such as:
>> >> > >>
>> >> > >> (1) N out of M
>> >> > >>
>> >> > >> (2) The two most important requests completed
>> >> > >>
>> >> > >> (3) A Boolean condition operating upon process variables
>> >> > >>
>> >> > >> > >>
>> >> > >> Not all activities must complete in order the enclosing
>> >> > flow activity
>> >> > >> to complete. The way to identify that an enclosed activity
>> did not
>> >> > >> complete is to propagate faults. We may distinguish between
>> severe
>> >> > >> faults and those that can be ignored. Severe faults cause the
>> >> > >> enclosing flow activity (or more precisely, enclosing
>> scope) to
>> >> > >> terminate the flow activity, including all active concurrent
>> >> > >> activities, and corresponding fault handler may be
>> >> > initiated. Other
>> >> > >> faults may be ignored - the flow activity is "informed" that a
>> >> > >> concurrent activity did not complete but still allows other
>> active
>> >> > >> concurrent activities to continue with execution.
>> >> > >>
>> >> > >> > >>
>> >> > >> Ignore semantics
>> >> > >>
>> >> > >> =================
>> >> > >>
>> >> > >> Faults thrown within enclosed concurrent activities/scopes
>> and not
>> >> > >> handled by local fault handlers are rethrown. Enclosing
>> >> > <flow> element
>> >> > >> decides which of these rethrown faults can be ignored. This
>> new
>> >> > >> "ignore" semantics should be part of the completion
>> condition and
>> >> > >> should apply to all enclosed activities. This new
>> >> > semantics does not
>> >> > >> introduce a new fault handling mechanism. It is needed for
>> >> > identifying
>> >> > >> how many of the enclosed activities failed.
>> >> > >>
>> >> > >> > >>
>> >> > >> > >>
>> >> > >> Proposed syntax
>> >> > >>
>> >> > >> ================
>> >> > >>
>> >> > >> <flow standard-attributes>
>> >> > >>
>> >> > >> standard-elements
>> >> > >>
>> >> > >> <completionCondition/>?
>> >> > >>
>> >> > >> <links>?
>> >> > >>
>> >> > >> <link name="ncname">+
>> >> > >>
>> >> > >> </links>
>> >> > >>
>> >> > >> activity+
>> >> > >>
>> >> > >> </flow>
>> >> > >>
>> >> > >> > >>
>> >> > >> <completionCondition>
>> >> > >>
>> >> > >> <conditions branch="xsd:integer"?
>> >> > >>
>> >> > >> expression=xpath?/>?
>> >> > >>
>> >> > >> <ignoreFaults>?
>> >> > >>
>> >> > >> <fault name="qname"? value="ncname"?/>*
>> >> > >>
>> >> > >> <ignoreAll/>?
>> >> > >>
>> >> > >> </ignoreFaults>
>> >> > >>
>> >> > >> </completionCondition>
>> >> > >>
>> >> > >> > >>
>> >> > >> Attribute branch is used to specify a condition of flavor
>> >> > "wait for
>> >> > >> /N/ out of /M/ activities to complete", or more precisely
>> value N.
>> >> > >> Attribute expression is used to specify a Boolean
>> >> > condition operating
>> >> > >> upon process variables or a condition of flavor "the two most
>> >> > >> important requests completed".
>> >> > >>
>> >> > >> > >>
>> >> > >> Both conditions ( branch and expression) may be specified
>> >> > at the same
>> >> > >> time. They will be checked when one instance of the scope
>> activity
>> >> > >> reaches the end. If at least one condition evaluates to
>> true all
>> >> > >> active instances will be terminated.
>> >> > >>
>> >> > >> > >>
>> >> > >> Element <ignoreFaults> specifies faults that may be
>> >> > ignored. Element
>> >> > >> fault is used to specify a fault which may be ignored
>> >> > (fault name and
>> >> > >> fault data may be specified). Element <ignoreAll> would
>> >> > mean that all
>> >> > >> faults thrown/rethrown by any concurrent activity/scope may be
>> >> > >> ignored. If this element is specified <fault> element must
>> >> > be omitted.
>> >> > >>
>> >> > >> > >>
>> >> > >> Completion condition failure
>> >> > >>
>> >> > >> =============================
>> >> > >>
>> >> > >> A new standard fault, e.g. completionConditionFailure,
>> should be
>> >> > >> introduced to notify that the completion condition of a
>> >> > flow activity
>> >> > >> evaluated to false (note: all concurrent activities have been
>> >> > >> completed). The fault is thrown in the scope enclosing the
>> >> > flow element.
>> >> > >>
>> >> > >> > >>
>> >> > >> Completion condition and links
>> >> > >>
>> >> > >> ==============================
>> >> > >>
>> >> > >> There should be no difference between a flow activity with a
>> >> > >> completion condition and a flow activity without
>> >> > completion condition.
>> >> > >> For example, if the completion condition fails all links
>> >> > leaving the
>> >> > >> flow activity should have value "false" (or be reverted to
>> >> > a negative
>> >> > >> status).
>> >> > >>
>> >> > >> > >>
>> >> > >> There are just a few additional rules:
>> >> > >>
>> >> > >> (1) Let's assume enclosed activity A is the source of a
>> >> > link. If the
>> >> > >> completion condition evaluates to true and activity A is
>> >> > not completed
>> >> > >> it will be terminated and the value of the link will be
>> >> > set to "false".
>> >> > >>
>> >> > >> (2) Let's assume enclosed activity A is the source of a
>> >> > link and the
>> >> > >> activity failed but the fault is "ignored" by the enclosing
>> flow
>> >> > >> activity. The value of the link will be set to "false".
>> >> > >>
>> >> > >> > >>
>> >> > >> New function for completion condition of flavor "the two most
>> >> > >> important requests completed"
>> >> > >>
>> >> > >>
>> >> > ==============================================================
>> >> > ==============================
>> >> > >>
>> >> > >>
>> >> > >> For completion conditions of flavor "the two most
>> >> > important requests
>> >> > >> completed" standard attribute "name" must be specified for all
>> >> > >> enclosing activities in order to be able to distinguish
>> them. In
>> >> > >> addition a new function, e.g. isCompleted('activityName')
>> must be
>> >> > >> introduced. The semantics of the function is: if activity
>> >> > completed
>> >> > >> successfully the function returns value true.
>> >> > >>
>> >> > >> > >>
>> >> > >> Example
>> >> > >>
>> >> > >> <completionCondition expression=
>> >> > >>
>> >> > >> "isCompleted('A') AND isCompleted('B')"
>> > >>
>> >> > >> </completionConditions>
>> >> > >>
>> >> > >> > >>
>> >> > >> > >>
>> >> > >> Regards,
>> >> > >>
>> >> > >> > >>
>> >> > >> Ivana
>> >> > >>
>> >> > >> > >>
>> >> > >> -----Original Message-----
>> >> > >> *From:* Alex Yiu [mailto:alex.yiu@oracle.com]
>> >> > >> *Sent:* Samstag, 11. September 2004 00:49
>> >> > >> *To:* Axel Martens
>> >> > >> *Cc:* 'edwink@collaxa.com
>> >> > <mailto:edwink@collaxa.com>'; Trickovic,
>> >> > >> Ivana; 'satisht@microsoft.com
>> <mailto:satisht@microsoft.com>';
>> >> > >> 'wsbpel@lists.oasis-open.org
>> >> > >> <mailto:wsbpel@lists.oasis-open.org>'; Alex Yiu
>> >> > >> *Subject:* Re: [wsbpel] Issue 6 - Rough draft of
>> >> > proposal for vote
>> >> > >>
>> >> > >>
>> >> > >> Hi, Axel,
>> >> > >>
>> >> > >> Thanks for liking parts of my proposal so far.
>> >> > >> Actually, the idea of my proposal is borrowed from a
>> part of
>> >> > >> presentation from Ivana and Dieter Roller in March F2F.
>> I just
>> >> > >> generalize it to apply to <flow> also.
>> >> > >>
>> >> > >> About using links or not:
>> >> > >> I don't have a huge opposition to Axel's proposal
>> >> > which enriches
>> >> > >> the semantics of joinCondition evaluation. However, it
>> >> > is not that
>> >> > >> difficult for people to make mistakes in joinCondition.
>> >> Look at
>> >> > >> the 2-out-of-3 example. The join condition already gets so
>> >> > >> complicated. If people make a mistake in their
>> >> > joinCondition, the
>> >> > >> whole flow can get struck for no good reasons. (The
>> >> > >> completeCondition approach will less likely to have
>> >> > the whole flow
>> >> > >> struck. Because, it does not introduce a new parallel
>> >> > activity in
>> >> > >> the flow). But, if this is what Petri-net-oriented and
>> >> > >> control-link-oriented audience really want, I can
>> >> > accept it in a
>> >> > >> sense, as long as this is not the only way to achieve
>> similar
>> >> > >> business logic.
>> >> > >>
>> >> > >> About static vs dynamic parallelism:
>> >> > >> Static parallelism is basically <flow> construct in
>> >> > BPEL. Dynamic
>> >> > >> parallelism is "parallel forEach" or "bundle". Issue 4
>> >> > and 147 are
>> >> > >> related issues.
>> >> > >> >
>> >> http://www.choreology.com/external/WS_BPEL_issues_list.html#Issue4
>> >> > >> >
>> >> http://www.choreology.com/external/WS_BPEL_issues_list.html#Issue147
>> >> > >>
>> >> > >> About "Terminating still running tasks versus
>> proceeding in
>> >> > >> control flow while those tasks are
>> >> > >> still running":
>> >> > >> I am not 100% that I understand your question. Let me
>> try to
>> >> > >> answer it anyway. The completeCondition is about
>> triggering
>> >> > >> termination of still-running tasks. The "proceeding in
>> control
>> >> > >> flow" (if I understand you correctly) will be handled
>> >> > by an outter
>> >> > >> flow. [I guess it is related to (hotel and (train or
>> >> > plane)) flow??]
>> >> > >>
>> >> > >> About changes of "forcedTermination" fault handler:
>> >> > >> If you got a chance to see some recent emails on Issue
>> >> > 135, Satish
>> >> > >> has recently suggested to remove the notion
>> >> "forcedTermination"
>> >> > >> fault and replace its fault handler with cancelHandler.
>> Frank,
>> >> > >> Yaron, Edwin and I all agree with this direction. Because,
>> >> > >> overloading fault with the concept of
>> "forcedTermination" is a
>> >> > >> "false economy" and it creates quite a bit of
>> >> > unnecessary confusion.
>> >> > >>
>> >> > >> I don't think we should go back to this route or even
>> further
>> >> > >> overload the "forcedTermination" fault handler
>> >> > semantics. Because,
>> >> > >> fault handling is way too generic and the changes you
>> >> mentioned
>> >> > >> will create even more confusion. (e.g. Will this
>> >> > change of marking
>> >> > >> as "completed" apply to all "forcedTermination" fault
>> >> handler /
>> >> > >> cancel handler of all scopes? )
>> >> > >>
>> >> > >> I guess most of us agree that we should have a new
>> >> mechanism to
>> >> > >> kill / do an early completion of a flow in a nice and
>> >> > clean way.
>> >> > >> However, overloading a standard fault handler does not
>> >> > seem to be
>> >> > >> the best one. I would rather introduce a construct
>> >> > which is very
>> >> > >> specific to <flow> or parallel-forEach. For example, this
>> >> > >> <completeCondition> construct or maybe a new activity
>> called
>> >> > >> <completeFlow />. I will send out more emails on
>> >> > joint thinking
>> >> > >> of both Issue 6 and Issue 135. Please stay tuned.
>> >> > >>
>> >> > >>
>> >> > >> Thanks!
>> >> > >>
>> >> > >>
>> >> > >>
>> >> > >> Regards,
>> >> > >> Alex Yiu
>> >> > >>
>> >> > >>
>> >> > >> Axel Martens wrote:
>> >> > >>
>> >> > >>>
>> >> > >>> Hi,
>> >> > >>>
>> >> > >>> I like the simplicity of the syntax of Alex's
>> >> > proposal. Although,
>> >> > >>> for me it is quite easy to model in terms of links and
>> join
>> >> > >>> conditions, and I want to keep my proposal alive
>> >> > (because of the
>> >> > >>> minimal changes to BPEL's syntax and semantics), it
>> >> > looks like a
>> >> > >>> nice macro to provide more convenience to the customers.
>> >> > >>>
>> >> > >>> Alex, could you shortly explain to me, what do you
>> >> > mean by static
>> >> > >>> and dynamic parallelism? How do you handle the two
>> >> > different cases
>> >> > >>> after evaluating the completeCondition: Terminating
>> >> > still running
>> >> > >>> tasks versus proceeding in control flow while those
>> tasks are
>> >> > >>> still running (Sorry, I missed your previous emails)?
>> >> > >>>
>> >> > >>> I agree to Alex's opinion, that we need a mechanism to
>> kill
>> >> > >>> parallel flow nice and clean. This could be done
>> >> > either by a new
>> >> > >>> mechanism which does not throw a fault or by changing
>> the way
>> >> > >>> fault are handled. I have discussed already an example
>> of the
>> >> > >>> second case with Ivana, and I like to tell you, what I
>> >> have in
>> >> > >>> mind. Look at the following example:
>> >> > >>>
>> >> > >>> <scope name="scopeFlow">
>> >> > >>> ...
>> >> > >>> <flow>
>> >> > >>> <link name="linkA"/>
>> >> > >>> <link name="linkB"/>
>> >> > >>>
>> >> > >>> <scope name="scopeA">
>> >> > >>> ...
>> >> > >>> <invoke name="A" ...>
>> >> > >>> <source linkName="linkA" ...>
>> >> > >>> </invoke>
>> >> > >>> </scope>
>> >> > >>>
>> >> > >>> <scope name="scopeB">
>> >> > >>> ...
>> >> > >>> <invoke name="B" ...>
>> >> > >>> <source linkName="linkB" ...>
>> >> > >>> </invoke>
>> >> > >>> </scope>
>> >> > >>>
>> >> > >>> <throw name="C" faultName="bpws:forcedCompletion"
>> >> > >>> joinCondition="linkA OR linkB"
>> >> > >>> joinEvaluation="immediate">
>> >> > >>> <target linkName="linkA" ...>
>> >> > >>> <target linkName="linkB" ...>
>> >> > >>> </throw>
>> >> > >>>
>> >> > >>> </flow>
>> >> > >>> </scope>
>> >> > >>>
>> >> > >>> First, I explain the situation: In the example above,
>> >> > activity C
>> >> > >>> will be executed if one of the two activities A and B was
>> >> > >>> successfully completed. Activity C throws the fault
>> >> > >>> "forcedCompletion". Like each other fault, this
>> >> > forces the scope
>> >> > >>> "scopeFlow" to terminate still running activities.
>> >> > Assume, there
>> >> > >>> was a fault handler defined in this scope which
>> >> > catches the fault
>> >> > >>> "forcedCompletion" (omitted in here), the process
>> >> > continues after
>> >> > >>> scope "scopeFlow". A problem arises, if scope
>> >> > "scopeFlow" should
>> >> > >>> be compensated. Because it was exited from a fault
>> >> handler, no
>> >> > >>> compensation handler was installed.
>> >> > >>>
>> >> > >>> Now, I explain my solution: In the example, I have
>> >> > chosen a new
>> >> > >>> "standard" fault name: "forcedCompletion". The only
>> necessary
>> >> > >>> change is to allow a fault handler that catches this
>> fault to
>> >> > >>> install a compensation handler for the same scope,
>> >> > i.e. to mark
>> >> > >>> the scope "scopeFlow" as "completed" instead of "exited".
>> >> > >>>
>> >> > >>> The standard compensation mechanism will only undo those
>> >> > >>> ("scoped") activities within the scope, which
>> >> > actually have been
>> >> > >>> successfully completed, i.e. scopeA or scopeB or may
>> be both.
>> >> > >>>
>> >> > >>> Axel.
>> >> > >>> ----------------------------------------
>> >> > >>> Axel Martens
>> >> > >>>
>> >> > >>> Post Doc Researcher
>> >> > >>> Component Systems Group
>> >> > >>> IBM TJ Watson Research Center
>> >> > >>> Hawthorne, NY (USA)
>> >> > >>> Phone: (914) 784-7480
>> >> > >>> E-mail: amarten@us.ibm.com <mailto:amarten@us.ibm.com>
>> >> > >>>
>> >> > >>>
>> >> > >>> *Alex Yiu <alex.yiu@oracle.com>
>> <mailto:alex.yiu@oracle.com>*
>> >> > >>>
>> >> > >>> 09/10/2004 12:10 AM
>> >> > >>>
>> >> > >>> > >>> To
>> >> > >>> Alex Yiu <alex.yiu@oracle.com>
>> >> > <mailto:alex.yiu@oracle.com>
>> >> > >>> cc
>> >> > >>> "Trickovic, Ivana" <ivana.trickovic@sap.com>
>> >> > >>> <mailto:ivana.trickovic@sap.com>, Axel
>> >> > Martens/Watson/IBM@IBMUS,
>> >> > >>> "'edwink@collaxa.com'" <mailto:%27edwink@collaxa.com%27>
>> >> > >>> <edwink@collaxa.com> <mailto:edwink@collaxa.com>,
>> >> > >>> "'satisht@microsoft.com'"
>> >> <mailto:%27satisht@microsoft.com%27>
>> >> > >>> <satisht@microsoft.com> <mailto:satisht@microsoft.com>,
>> >> > >>> "'wsbpel@lists.oasis-open.org'"
>> >> > >>> <mailto:%27wsbpel@lists.oasis-open.org%27>
>> >> > >>> <wsbpel@lists.oasis-open.org>
>> >> > >>> <mailto:wsbpel@lists.oasis-open.org>, Alex Yiu
>> >> > >>> <alex.yiu@oracle.com> <mailto:alex.yiu@oracle.com>
>> >> > >>> Subject
>> >> > >>> Re: [wsbpel] Issue 6 - Rough draft of proposal
>> for vote
>> >> > >>>
>> >> > >>>
>> >> > >>>
>> >> > >>> > >>>
>> >> > >>>
>> >> > >>>
>> >> > >>>
>> >> > >>>
>> >> > >>>
>> >> > >>> Hi,
>> >> > >>>
>> >> > >>> Here are some examples how to use completeCondition to
>> >> express
>> >> > >>> similar business logic in Axel's previous email:
>> >> > >>>
>> >> > >>> (A) "Select one out of three" example:
>> >> > >>> <flow>
>> >> > >>> <completeCondition *branch="1"* />
>> >> > >>> <invoke name="CheckAirlineA" ... />
>> >> > >>> <invoke name="CheckAirlineB" ... />
>> >> > >>> <invoke name="CheckAirlineC" ... />
>> >> > >>> </flow>
>> >> > >>>
>> >> > >>>
>> >> > >>> (B) "Select two out of three" example:
>> >> > >>> <flow>
>> >> > >>> <completeCondition *branch="2"* />
>> >> > >>> <invoke name="AskRefereeA" ... />
>> >> > >>> <invoke name="AskRefereeB" ... />
>> >> > >>> <invoke name="AskRefereeC" ... />
>> >> > >>> </flow>
>> >> > >>>
>> >> > >>> As you guys can see, the completeCondition declaration is
>> >> very
>> >> > >>> straight forward and simple. No complicated links and
>> >> > >>> joinCondition usage.
>> >> > >>>
>> >> > >>> (C) "(Plane or Train) and Hotel" example: It would
>> become two
>> >> > >>> flow constructed (nested).
>> >> > >>>
>> >> > >>>
>> >> > >>> <assign> ... <to variable="planeResult"></assign>
>> >> > >>> <!-- initialize "planeResult" with NOT-OK value -->
>> >> > >>> <assign> ... <to variable="trainResult"></assign>
>> >> > >>> <!-- initialize "trainResult" with NOT-OK value --> *
>> >> > >>> <flow name="checkIterinary">*
>> >> > >>> *<flow name="PlaneOrPlane">*
>> >> > >>> <completeCondition>
>> >> > >>> fn:planeOK(planeResult) *or*
>> >> > fn:trainOK(trainResult)
>> >> > >>> </completeCondition>
>> >> > >>> <invoke name="CheckPlane"
>> >> > outputVariable="planeResult" ... />
>> >> > >>> <invoke name="CheckTrain"
>> >> > outputVariable="trainResult" ... />
>> >> > >>> *</flow> *
>> >> > >>> <invoke name="checkHotel" /> *
>> >> > >>> </flow>
>> >> > >>> <switch name="bookingSwitch">*
>> >> > >>> <case>
>> >> > >>> <condition>
>> >> > >>> (fn:planeOK(planeResult) *or*
>> fn:trainOK(trainResult))
>> >> > >>> *and* fn:hotelOK(hotelResult)
>> >> > >>> </condition>
>> >> > >>> <invoke name="invokeBooking" ... />
>> >> > >>> </case>
>> >> > >>> <otherwise>
>> >> > >>> <invoke name="writeInformation" ... />
>> >> > >>> </otherwise> *
>> >> > >>> </switch>*
>> >> > >>>
>> >> > >>>
>> >> > >>> Please note that regardless whether we pick a
>> link-oriented
>> >> > >>> approach or completeCondition approach:
>> >> > >>>
>> >> > >>> * The initialization of result variables are
>> >> > needed because
>> >> > >>> of potential cancellation of one of the invoke
>> between
>> >> > >>> train and plane
>> >> > >>> * The "fn:*()" represents the logic to determine
>> >> whether a
>> >> > >>> traveling resource is available. They are used in
>> >> either
>> >> > >>> the transitionCondition of links or the
>> condition of
>> >> > >>> switch/case.
>> >> > >>>
>> >> > >>> As you guys see, we don't need declare to six links. The
>> >> > >>> completeCondition and case-condition are much simpler
>> >> > and easier
>> >> > >>> to understand.
>> >> > >>>
>> >> > >>> I attach a diagram to illustrate the above flows.
>> >> > >>>
>> >> > >>> I guess we can still more time in terms of refiniment of
>> >> > >>> joinCondition evaluation. However, I don't think that
>> >> > should be
>> >> > >>> the only approach to achieve complete condition related
>> >> logic.
>> >> > >>>
>> >> > >>>
>> >> > >>> Thanks!!!
>> >> > >>>
>> >> > >>> Regards,
>> >> > >>> Alex Yiu
>> >> > >>>
>> >> > >>>
>> >> > >>>
>> >> > >>>
>> >> > >>> Alex Yiu wrote:
>> >> > >>>
>> >> > >>> Hi,
>> >> > >>>
>> >> > >>> +1 to what Ivana said in general.
>> >> > >>>
>> >> > >>> Few points to add:
>> >> > >>>
>> >> > >>> * Axel's proposed enhancement to control links
>> evaluation
>> >> > >>> works to an extent for static parallelism > (e.g.
>> >> <flow>).
>> >> > >>> However, control links do not work well in dynamic
>> >> > >>> parallelism (e.g. "parallel forEach" or
>> >> > "bundle"). I think
>> >> > >>> the notion of completeCondition (borrowed from
>> Ivana
>> >> and
>> >> > >>> DK) is general enough and it should be applied
>> to both
>> >> > >>> static and dynamic parallelism. A general
>> >> > completeCondition
>> >> > >>> mechanism will be easier for BPEL users to learn.
>> >> > >>> * Even in a pure static parallelism case,
>> >> > completeCondition
>> >> > >>> has much better code clarity. It is more
>> declarative
>> >> and
>> >> > >>> easier for BPEL users to understand. It will
>> eliminate
>> >> > >>> significant amount of joinCondition
>> >> > programming, which may
>> >> > >>> be error prone. (I will send another email later to
>> >> show
>> >> > >>> how completeCondition can be used to express the
>> same
>> >> > >>> semantics of Axel's example).
>> >> > >>> * In one of my previous emails, I also tried to
>> >> > use a "macro"
>> >> > >>> way to illustrate how outstanding running flows
>> can be
>> >> > >>> cancelled by throwing a fault within a scope. The
>> >> > >>> illustration has the same compensation handler
>> >> > installation
>> >> > >>> problem that Ivana has pointed out. The
>> "illustraction
>> >> > >>> macro" does NOT carry a desirable and intended
>> >> > semantics.
>> >> > >>> We need to create / describe a new mechanism to
>> cancel
>> >> > >>> parallel flow without throwing a fault. (That
>> >> > was discussed
>> >> > >>> briefly between Edwin and me at Oracle).
>> >> > >>>
>> >> > >>>
>> >> > >>> Thanks!
>> >> > >>>
>> >> > >>>
>> >> > >>> Regards,
>> >> > >>> Alex Yiu
>> >> > >>>
>> >> > >>>
>> >> > >>>
>> >> > >>> Trickovic, Ivana wrote:
>> >> > >>> Axel,
>> >> > >>> > >>> I find the idea interesting. In fact, I was
>> >> discussing the
>> >> > >>> completion condition issue with Dieter Koenig during
>> >> > the last f2f
>> >> > >>> meeting and his suggestion was also to try to resolve
>> >> > this issue
>> >> > >>> using links. And we identified that several changes need
>> >> to be
>> >> > >>> done, including removing restriction for
>> >> > jonCondition, that "the
>> >> > >>> join condition is evaluated as soon as all incoming
>> >> > links of the
>> >> > >>> activity are determined" - so definitely "immediate"
>> >> semantics
>> >> > >>> needs to be introduced.
>> >> > >>> > >>> I have the following comments on your
>> proposal.
>> >> > >>> 1. In your proposal you are using a fault
>> >> > >>> (bpws:forcedTermination) to terminate all active parallel
>> >> > >>> branches. But this changes the outcome of the flow
>> >> > activity. It
>> >> > >>> will always end abnormally and compensation handler
>> (if it is
>> >> > >>> defined) will never be installed. Although completion
>> >> > condition
>> >> > >>> has evaluated to true and needed activities have
>> completed
>> >> the
>> >> > >>> enclosing flow activity will end abnormally. Is this
>> really
>> >> > >>> intended semantics?
>> >> > >>> > >>> 2. Your proposal does not address some pain
>> >> points.
>> >> > For example,
>> >> > >>> in case of "N out of M", N<M there many possible
>> >> "variations":
>> >> > >>> (A) One enclosed activity may experience problems but
>> >> > the <flow>
>> >> > >>> activity may succeed
>> >> > >>> (B) One of enclosed activities may experience a severe
>> error,
>> >> > >>> which may have impact on the <flow> activity
>> >> > >>> The question is what to do with running activities?
>> >> > In the latter
>> >> > >>> case, reasonable behavior would be: if one enclosed
>> >> > activity does
>> >> > >>> not succeed other running activities should be
>> >> > cancelled and the
>> >> > >>> flow activity should try to recover. In the former
>> case, we
>> >> > >>> should allow active parallel activities to complete
>> >> > their work.
>> >> > >>> This is not supported in your proposal.
>> >> > >>> > >>> Regards,
>> >> > >>> > >>>
>> >> > >>> Ivana
>> >> > >>>
>> >> > >> [stuff deleted]
>> >> > >>
>> >> > >
>> >> >
>> >> > To unsubscribe from this mailing list (and be removed from
>> >> > the roster of the OASIS TC), go to
>> >> > http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/le
>> >> > ave_workgroup.php.
>> >> >
>> >>
>> >> To unsubscribe from this mailing list (and be removed from the
>> roster
>> >> of the OASIS TC), go to
>> >>
>> http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgroup.php.
>>
>> >>
>> >>
>> >
>> > To unsubscribe from this mailing list (and be removed from the roster
>> > of the OASIS TC), go to
>> >
>> http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgroup.php.
>>
>> >
>> >
>> >
>>
>> To unsubscribe from this mailing list (and be removed from the roster
>> of the OASIS TC), go to
>> http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgroup.php.
>>
>>
>
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