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CAiSE 2013 - Valencia, Spain
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User
Business Process Definition
Business Process Engine
Process Instances
2 1
2
1 Modelling
Enactment
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User
Business Process Definition
Business Process Engine
Process Instances
2 1
2
1 Modelling
Enactment
Evolutionary Ad-hoc
[van der Aalst, 2001]
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Tow Trucks Call Center Garages Paramedics Taxis
A Motorist
RoSAS
• RoSAS : Roadside Assistance as a Service.
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• RoSAS defines the control-flow.
• Providing roadside assistance is a long lived process.
• Unpredictability.
• Example 1: Ms. Swan (a motorist) requests to delay the towing until a
taxi picks her up (its raining now and the car is the only shelter).
• Example 2: Mr. Doe (another motorist) requests a notification once the
towing is complete (he drives an Aston Martin v12).
• Both above scenarios.
• Are not captured by RoSAS in its business process definition because
those are unpredictable or are not commonly occurred.
• Need be supported if possible to enhance RoSAS’s reputation due to
customer oriented nature of the business.
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• WS-BPEL - the de-facto standard.
• Block structured control-flow (imperative programming).
• Have been criticized for lack of flexibility.
• Proposed improvements
• Template Customization, Aspect-orientation, ...
• Template customization
• A technique used to generate a highly optimized fitting process that suits
the situation in demand from a pre-defined template.
E.g., [Mietzner, 2008], [Ardagna, 2007]
• However, requires re-generating a new process.
• Aspect-Orientation
• A technique used to weave variation points to a core business process
(similar to Aspect oriented programming)
E.g., [Charfi, 2007], [Michiel, 2009]
• However, requires identifying the fixed and volatile parts.
• Other solutions
• Constraint-satisfaction. E.g., DecSerFlow [Pesic, 2006]
• Dynamic Changes. E.g., Skip/Retry [Fang, 2008]
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• The tight coupling between activities/tasks of a business process as enforced
by the modelling language.
• The over-specification of control-flow. An unnecessary restriction to adapt
process instances.
tRequestTow tTow
• Above denotes that, the pre-condition of task tTow is the completion of task
tRequetTow.
• What if a new dependency need to be introduced during the runtime?
• Looks like an over-specification of task dependencies.
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• Be explicit about the dependencies in the specification.
• Tasks need to be decoupled by localizing the dependencies.
• Event-driven task-decoupling.
tRequestTow tTow
Post-conditions Pre-conditions
Task tRequestTow {
preEP "eComplaintRcvd AND eWithinTowZone";
postEP "eTowReqd";
}
Task tTow {
preEP "eTowReqd";
postEP "eTowSuccess XOR eTowFailed";
}
An Event Pattern
Loose-coupling
Event-driven task decoupling
AND eTaxiProvided";
Task tSendSpecialNotification{
preEP “eTowSuccess";
postEP “SpecialNotifcationSent";
}
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T1 T1
T1 T1
T1 T1
T1 T1
T1 T1
T1 T1
T1
Event X
Event Y
Process Instance id=p0123
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• Tasks localize their pre- and post-conditions as patterns of events.
• Tasks are declaratively defined in modular units called Behaviour Units.
• A Process Definition is a collection of references to such Behaviour Units.
(Process re-use [Kapuruge, WISE 2011])
• A Process Definition also specifies the Condition of Start (CoS) and Condition
of Termination (CoT)
• Constraints are specified in both Behaviour Units and Process Definitions.
(Controlled-flexibility [Kapuruge, SCC 2011])
Behaviour bTowing{ Task CO.tRequestTow { preEP "eComplaintRcvd * eWithinTowZone"; postEP "eTowReqd"; } Task TT.tTow { preEP "eTowReqd"; postEP "eTowSuccess ^ eTowFailed"; } Task CO.tPay { preEP "eTowSuccess"; postEP "eTTPaid"; } Const c1: "(eTowSuccess>0) -> (eTTPaid>0)";}
ProcessDefinition pdAssist { CoS "eComplaintRcvd"; CoT "eMMNotifDone"; BehaviourRef bComplaining; BehaviourRef bTowing; BehaviourRef bRepairing; BehaviourRef bTaxiProviding; Const c5:"(eComplaintRcvd>0)->
(eComplainAcked>0)";}
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Behavior Unit Task
RoleOrganisation Event Pattern Pre/Post
Conditions
Process Definition Refer Refer
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• Existing service orchestration runtimes (e.g., Apache ODE, Active VOS) are
designed to execute tightly-coupled control-flows.
• If used to enact Serendip processes, the flexibility at runtime is limited.
• A new service orchestration runtime is required.
• Models@runtime + Pub-sub mechanism.
AMS : Adaptation Management System
FS: Functional System
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• Individual models corresponding to tasks (TiM) and process instances (PiM)
are maintained in Model-Provider-Factory (MPF).
• These models could be individually adapted (explained later).
• An EPC (Event-driven Process Chain) view is dynamically constructed based
on up-to-date models [Kapuruge, 2012]
Model Provider Factory
p002p003p004
p001Ru
ntim
e
Mod
els
PiM
TiM
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• Event-cloud, a repository of events.
• Publishers e.g., Tasks, can publish events in the event-cloud.
• Subscribers e.g., Tasks, Process Instances can subscribe to these events.
• Upon completion of subscribed event-pattern, the subscriber is notified.
• Subscribers can be dynamically added.
• Event-patterns can be subjected to late changes.
s1
e
ee
e
ee
e
s2
p001
s3
The Event Cloud
e
Publish
Publisher
e.g., TiM
Notify
Subscriber
e.g., TiM, PiM
Subscribe
e
e
ee
...
Event
Repo
Subscriber List
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• Designed to systematically manage adaptations.
• To ensure process consistency and business integrity.
• Adaptation commands can be issued as a batch (Adaptation Script).
• A Script can contain multiple adaptation commands (steps).
INST: p124{
updateTaskOfProcessInst tId= "tTow" prop="postEP"
value="(eTowSuccess AND (eInMetro XOR eInRegional)) XOR
eTowFailed " ;
addTaskToProcessInst tId= "tSendSpecialNotif" preEP=" eInMetro "
obligRole="CO" ;
}
• Adaptation commands of a single script are
• Carried out in a single transaction (to ensure ACID properties).
• Carried out in safe states (to ensure state-consistency of models).
• Rejected if not possible.
Process instance id
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• Evaluated against Change Patterns [Weber et al., 2007]
• Change Patterns -> Patterns that should be supported by an adaptive
process aware information system.
• All adaptation patterns (AP) and patterns for pre-defined changes (PP) can be
supported. Some change support features (CF) are not supported.
AP 1 2 3 4 5 6 7 8 9 10 11 12 13
PP 1 2 3 4
CF 1.a 1.b 1.c 2 3 4 5 6
X = Not Supported
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• Evaluated against Apache ODE (Both SOR and ODE uses Axis2 as the
framework).
• Slightly slower than Apache ODE.
ODE SOR
Avg Response Time
(σ = Std. Dev)
Δt1 = 181.71 ms
(σ = 0.30)
Δt2 = 191.61 ms
(σ = 0.12)
Percentage Performance Lost (PPL) = Δ𝑡2
− Δ𝑡1
Δ𝑡1 x 100 % = 5.448%
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• [van der Aalst., 2001] : van der Aalst, W.M.P.: Exterminating the Dynamic Change Bug: A Concrete Approach to
Support Workflow Change. Information Systems Frontiers. Vol. 3,pp. 297-317 (2001)
• [Mietzner, 2008]: Mietzner, R., Leymann, F.: Generation of BPEL Customization Processes for SaaS Applications
from Variability Descriptors. In: Services Computing (SCC), pp. 359-366. (2008)
• [Ardagna, 2007]: Ardagna, D., Comuzzi, M., Mussi, E., Pernici, B., Plebani, P.: PAWS: A Framework for Executing
Adaptive Web-Service Processes. IEEE Software. Vol. 24,pp. 39-46 (2007)
• [Charfi, 2007] : Charfi, A., Aspect-Oriented Workow Languages: AO4BPEL and Applications. Darmstadt University
of Technology, Darmstadt, Germany. (2007)
• [Michiel, 2009]: Michiel, K., Chang-ai, S., Marco, S., Paris, A.: VxBPEL: Supporting variability for Web services in
BPEL. Information and Software Technology. Vol. 51,pp. 258-269 (2009)
• [Pesic, 2006]: Pesic, M., van der Aalst, W.M.P.: A Declarative Approach for Flexible Business Processes
Management. Business Process Management Workshops, pp. 169-180 (2006)
• [Fang, 2008]: Fang, R., Zou, Z.L., Stratan, C., Fong, L., Marston, D., Lam, L., Frank, D.: Dynamic Support for
BPEL Process Instance Adaptation. In: IEEE International Conference on Services Computing, pp. 327-334. IEEE
Computer Society, (2008)
• [Dadam, 2007]: Dadam, P., Reichert, M.U., Rinderle, S.B., Jurisch, M., Acker, H., Göser, K., Kreher, U., Lauer, M.:
ADEPT2 - Next Generation Process Management Technology. In: Fourth Heidelberg Innovation Forum. D.punkt
Verlag, (2007)
• [Kapuruge, WISE 2011]: Kapuruge, M., Colman, A., Han, J.: Achieving Multi-tenanted Business Processes in SaaS
Applications. In: Web Information System Engineering (WISE), pp. 143-157. Springer Berlin / Heidelberg, (2011)
• [Kapuruge, SCC 2011]: Kapuruge, M., Colman, A., Han, J.: Controlled flexibility in business processes defined for
service compositions. In: Services Computing (SCC) pp. 346-353. IEEE Press, (2011)
• [Kapuruge, 2012]: Kapuruge, M., Orchestration as Organisation. PhD Thesis, Swinburne University of Technology,
Melbourne. (2012)
• [Weber, 2007]:Weber, B., Rinderle, S., Reichert, M.: Change Patterns and Change Support Features in Process-
Aware Information Systems. Advanced Information Sys. Eng., pp. 574-588 (2007)
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