Workshop on Formal Aspects to Business Processes and Web ServicesSiedlce, 26 June 2007

Niels Lohmannnlohmann@informatik.hu-berlin.de

A Feature-Complete Petri NetSemantics for WS-BPEL 2.0

A Feature-Complete Petri NetSemantics for WS-BPEL 2.0

Workshop on Formal Aspects to Business Processes and Web ServicesSiedlce, 26 June 2007

Niels Lohmannnlohmann@informatik.hu-berlin.de

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A Feature-C

omplete Petri N

et Semantics for W

S-BPEL 2.0

WS-BPEL

Web Service Business Process Execution Language

Language to describe business processes implemented as Web services

Described as XML document

<process name="example"><sequence>

<receive partnerLink="p1" /><invoke partnerLink="p2" /><reply partnerLink="p1" />

</sequence></process>What does this mean?

What does this mean?

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Petri Net Semantics for WS-BPEL

Goal: a formal semantics for WS-BPEL

… to understand WS-BPEL

… to analyze WS-BPEL processes

Formal model: open workflow nets

workflow nets

+ interface

– structural constraints

= open workflow nets

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Example: <receive> Activity

initial

running

final

stop

stopped

failed

faulted

channel

variable

t1

t2

t3

t4

t5

t6

t7

x

x

x

x

x

y

x

v

faultName

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Example: <flow> Activity

A B

initial

final

stop

stopped

running

sync

t1 t3

t4

t5

t6

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New Features of WS-BPEL 2.0

Semantic clarifications

What happens during compensation?

Syntactic sugar

<repeatUntil> activity, inline validation, …

Some new activities and features

<forEach> activity, termination handlers, ...

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Implementation

BPEL2oWFN

Petri NetAPI

PatternRepository

Control/DataFlow Graph

AbstractSyntax Tree

meta model

static analysis pattern selection

Petri net model

BPEL process Petri net

Input Formats:

WS-BPEL 2.0BPEL4WS 1.1Abstract WS-BPEL 2.0BPEL4ChorWSDL 1.1

Output Formats:

Fiona oWFNLoLAPNMLINA, PEP, SPIN…

http://www.gnu.org/software/bpel2owfn

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Applications of the Semantics (1)

Open workflow nets allow for…

Analysis of the inner of the oWFN (w/o interface)

Deadlock freedom

(relaxed) Soundness

Temporal logics

…

Analysis results can be mapped back to WS-BPEL

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Tools4BPEL Tool Chain (1)

BPEL2oWFN

LoLALoLA2BPEL

WS-BPELProcess

Petri NetModel

WitnessPath

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Applications of the Semantics (2)

Open workflow nets allow for…

Analysis of the open workflow net

Consistency

Controllability

Partner synthesis

…

Synthesis results can be re-translated to WS-BPEL

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Tools4BPEL Tool Chain (2)

BPEL2oWFN

FionaoWFN2BPEL

WS-BPELProcess

oWFNModel

PartneroWFN

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Summary (1)

Feature-complete semantics for WS-BPEL 2.0

and its predecessor specification

Simplified patterns for important constructs

Case study:

Compiler BPEL2oWFN

3971,069Transitions

304,0076,261,648States

242410Places

New SemanticsOld Semantics

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Summary (2)

Petri net semantics allows to formally analyzeWS-BPEL processes

Analysis results can be re-translated into WS-BPEL

Complete tool chains help to “conceal” formal methods from the WS-BPEL designer

Danger: new semantics needed for future versionsWS-BPEL 2.1, WS-BPEL 3.0, WS-BPEL 4.0, …

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Questions?

A FEATURE-COMPLETEPETRI NET

SEMANTICSFOR

WS-BPEL 2.0