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Subject: Re: [wsbpel] Issue 6 - Rough draft of proposal for vote
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; satisht@microsoft.com;
> > 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.
> >
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