correctness ensuring process configuration: an approach based on partner synthesis

Correctness Ensuring Process Configuration:An Approach Based on Partner SynthesisWil van der Aalst (TU/e, QUT)Niels Lohmann (U-Rostock, TU/e)Marcello La Rosa (QUT)Jingxin Xu (QUT)

The need for configurable process models: CoSeLoG project

PAGE 1+/- 430 Dutch municipalities

The need for configurable process models: Suncorp case

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End to end process has between 250-1000 process steps

Sources: Guidewire reference models, GIO CISSS Project, CI US&S P4PI Project

Product Dev

• 25+ steps

Sales

• 50+ steps

Service

• 75+ steps

Claims

• 100+ steps

30variations

500steps

Home

Motor

Commercial

Liability

CTP / WC

Two variants of the same process …

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Variation points

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Action

Blocking

Activating

HidingBlocking

Activate

Hide/skip

Block

Configuration = limiting behavior !

Correctness of configurations

• Question 1: Is a particular configuration correct?

• Question 2:Is there a correct configuration?

• Question 3: How to characterize the set of all correct configurations?

• Question 4:How to auto-complete a configuration?

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Configurable Model + Configuration = Configured model

+ =

Can t3 be blocked?

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pI

p5

t7

p6

t8

pO

t2

p3

t1

p2

t4t5

p4

t6

p7

pI

p5

t7

p6

t8

pO

t2

p3

t1

p2

t4t5

p4

t6t3

p7

XOR-join

XOR-split

AND-join

AND-split

Flow

Place

Transition

Token

Block t1 and hide t3 ?

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p2

p3

p5

p8

t3

t1 t2

t4

t6

Prepare Travel Form(Secretary)

Prepare Travel Form(Employee)

ApproveTravel Form

(Admin)

RejectTravel Form

(Admin)

Submit Travel Form for Approval (Employee)

Request for change(Admin)

t7Check & Update Travel Form(Employee)

Arrange travel insurance (Employee)

p4

t5 τ

p6

p7

t9t8

p1

XOR-join

XOR-split

AND-join

AND-split

Flow

Place

Transition

Token

p2

p3

p5

p8

t3

t2

t4

t6

ApproveTravel Form

(Admin)

RejectTravel Form

(Admin)

Submit Travel Form for Approval (Employee)

Request for change(Admin)

t7Check & Update Travel Form(Employee)

p4

t5 τ

p6

p7

t9t8

τ

p1Prepare Travel Form(Employee

Block t4 also?

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p2

p3

p5

p8

t3

t1 t2

t4

t6

Prepare Travel Form(Secretary)

Prepare Travel Form(Employee)

ApproveTravel Form

(Admin)

RejectTravel Form

(Admin)

Submit Travel Form for Approval (Employee)

Request for change(Admin)

t7Check & Update Travel Form(Employee)

Arrange travel insurance (Employee)

p4

t5 τ

p6

p7

t9t8

p1

XOR-join

XOR-split

AND-join

AND-split

Flow

Place

Transition

Token

p2

p3

p5

p8

t3

t2

t6

Prepare Travel Form(Employee

ApproveTravel Form

(Admin)

RejectTravel Form

(Admin)

Submit Travel Form for Approval (Employee)

Request for change(Admin)

t7

p4

t5 τ

p6

p7

t9t8

τ

p1

Existing approaches

• Most approaches only consider the syntactical issues or simply create the configured model and analyze it (i.e., trail and error).

• Our earlier approach using a SAT solver is an exception to this rule, but is limited to free-choice WF-nets.

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W.M.P. van der Aalst, M. Dumas, F. Gottschalk, A.H.M. ter Hofstede, M. La Rosa, J. Mendling, Preserving Correctness During Business Process Model Configuration. In Formal Aspects of Computing (FACS). Vol. 22 No. 3-4, 2010.

New approach

• Based on partner synthesis developed in the Rostock group.

• Implemented in C-YAWL using Wendy.

• Advantages:1. No syntactical restrictions (i.e. beyond WF-nets

and free-choice).2. Complete characterization of all correct

configurations at design time: the so-called configuration guideline.

3. Computation time is moved from configuration time to design time.

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Open nets and weak termination

Open net:• Labeled Petri net without any

syntactical restrictions.• Special label:• Set of final markings, in this case

[p4].

Correctness notion:• weak termination: it is always

possible to reach a final marking (weaker than classical soundness)

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τ

Composition of open nets

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t11 t12 t21xy x

τ t14t13

t15

z

z

t22 z

p11

p12

p13

p14

p21

p22

p23

Ω ={[p14]} Ω ={[p23]}

(t12,t21)

(t14,t22)t13

(t15,t22)

p11

p12

p13

p14

p22

p23

τ

τ τ

τ

Ω ={[p14,p23]}

p21

=

Controllability

• An open net is controllable if there exists another open net such that their composition is weakly terminating.

• An open net is called a partner of another open net if their composition is weakly terminating.

• A controllable open net has at least one partner.• There are efficient techniques to check controllability

and to synthesize partners.[Karsten Wolf. Does My Service Have Partners?. T. Petri Nets and Other Models of Concurrency 2: 152-171 (2009)]

• These are implemented in Wendy. [Niels Lohmann, Daniela Weinberg. Wendy: A Tool to Synthesize Partners for Services. Petri Nets 2010: 297-307.]

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Controllability

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t11 t12 xy

τ t14t13 z

p11

p12

p13

Ω ={[p13]}

p14 = weakly terminating

partner??

Idea: good configuration = partner!

Configurable interface (allow by default)

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Configurable interface (block by default)

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Configuration guideline (allow by default)

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CG

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Configurable interface (block by default)

PAGE 18CG

Configuration guideline (allow by default)

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CG

Configuration guideline (allow by default)

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CG

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Configuration guideline (allow by default)

CG

Configuration guideline (allow by default)

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CG

Tool support

• YAWL editor− Creating C-YAWL models− Configuring C-YAWL models− Verification and auto-completion (using SAT solver

and/or Wendy)• YAWL engine• YAWL services

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Mapping(.cmap)

C-EPC model(.epml)

ConfiguredC-EPC (.epml)

EPC(.epml)

Questionnaire Model (.qml)

ConfiguredC-YAWL (.yawl)

YAWL Engine spec. (.yawl)

C-YAWL model(.yawl)

Quaestio

Mapper ProcessConfigurator

ProcessIndividualizer

Configurationmodel (.cml)

QuestionnaireDesigner

C-YAWL Editor

C-EPC Designer Process Merger

p2

p3

p5

p8

t3

t1 t2

t4

t6

Prepare Travel Form(Secretary)

Prepare Travel Form(Employee)

ApproveTravel Form

(Admin)

RejectTravel Form

(Admin)

Submit Travel Form for Approval (Employee)

Request for change(Admin)

t7Check & Update Travel Form(Employee)

Arrange travel insurance (Employee)

p4

t5 τ

p6

p7

t9t8

p1

C-YAWL

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C-YAWL

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Conclusion

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• New approach for ensuring the correctness of process configurations based on partner synthesis.

• Advantages:1. No syntactical restrictions (i.e. beyond WF-nets and free-

choice).2. Complete characterization of all correct configurations at

design time: the so-called configuration guideline.3. Computation time is moved from configuration time to

design time.• Implemented in C-YAWL using Wendy.

− Complete support for workflow configuration, verification, and enactment.

− Autocomplete, domain knowledge, etc.

More information

• www.processconfiguration.com(various references to configuration literature and a comprehensive toolset)

• www.yawlfoundation.org(YAWL has been extended to support configuration, cf. C-YAWL)

• service-technology.org(paper and tools - including Wendy - related to the analysis of services)

• www.win.tue.nl/coselog(webpage of the CoSeLoG project)

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