This presentation discusses techniques for modeling, analyzing, synthesizing, and characterizing service behavior. It introduces modeling service behavior formally using Petri nets and automata for precision. It covers analyzing behavior for compatibility using state space verification. It also discusses synthesizing partner behavior to ensure controllability and characterizing partners using operating guidelines for discovery and substitutability. A variety of problems are addressed including composition, adaptation, diagnosis, repair, and realizability.

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Behavior
of Services
Karsten Wolf
m3 techniques
for n∞ problems
UNIVERSITÄT ROSTOCK

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Service?
• Encapsulated functionality
• heterogenous platforms
• Self-explaining
• UDDI, ...
• Well defined interface
• WSDL
• Loosely coupled
• asynchronous communication
• binding via standardized protocols
•Main activity: composition
€
C T
B

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Behavior?
Semantics:
what does it
mean?
13m? $13?
1313
Nonfunctional:
how to transmit
-policies
-QoS
1313
Behavior:
when to
transmit 1313
Syntax:
how to
encode
<13> </13>
1313
Service

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This presentation:
• Part I: m3 techniques
0: modeling behavior
1: analysing behavior
2: synthesizing behavior
3: characterizing behavior
• Part II: n∞ problems
compatibility, controllability, substitutability, transformation, public
view generation, instance migration, uncontrollability diagnosis,
choreography repair, adaptation, test case generation, discovery,
composition, validation, realizability

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Modeling Behavior
Service
real world: WS-BPEL, BPMN, UML-ACT, ...
Model
formal semantics
Petri nets, automata, ...
Why?
precise meaning
independency of
language evolution
abstraction from
irrelevant details
find ambiguities/
inconsistencies
?€
?C ?T
!B !B[BPM 05,WS-FM 07,LNCS ToPNoC II]

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Modeling Behavior
Service
real world: WS-BPEL, BPMN, UML-ACT, ...
Model
formal semantics
Petri nets, automata, ...
Fact
We use feature
complete
semantics:
-links
-fault handling
-compensation
-events
?€
?C ?T
!B !B[BPM 05,WS-FM 07,LNCS ToPNoC II] implemented:
BPEL2oWFN

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1 Analying Behavior
= Compatibility
Service Service
?
implemented:
LoLA
several compatibility notions:
-deadlock freedom
-weak termination (always possible)
-strong termination (eventually will)
-coverage of activities
-other constraints
How?
state space
verification
[BPM 06,WS-FM 07]

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1 Analying Behavior
= Compatibility
Service Service
?
LoLA can do the job:
•soundness of 868 real business processes:
av. 4ms per process
•BPEL4Chor choreographies with
>1000 service instances
Why?
concurrency  partial order reduction
replicated instances symmetry method
acyclic behavior  sweep-line method
[BPM 06,WS-FM 07]

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2 Partner synthesis
Service
?
implemented:
(Fiona), Wendy
several controllability notions:
-centralized
-decentralized
-autonomous
[EMISA 05, LNCS ToPNoC II, IPL 08]

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2 Partner synthesis
Service
?
?€
?C ?T
!B !B
1
2
3 4
5
(1,-
)
!€
!C
!T
(1,C
)
(1,€),
(2,-)
(1,T
)
!T
!€
(1,CT
)
(1,C€),(2,C),(3,-),
(5,B)
!€
?B
!T
!C
!T
!C
!€
?B
!C
(1,T€),(2,T),(4,-),
(5,B)
(5,-)
(1,C€T),(2,CT),(3,T),(4,C),
(5,T)
deadlock

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2 Partner synthesis
Service
?
?€
?C ?T
!B !B
1
2
3 4
5
(1,-
)
!€
!C
!T
(1,C
)
(1,€),
(2,-)
(1,T
)
!€
(1,CT
)
(1,C€),(2,C),(3,-),
(5,B)
?B
!C
!T
!T
!C
!€
?B
(1,T€),(2,T),(4,-),
(5,B)
(5,-)
!€
!T
!C
(1,C€T),(2,CT),(3,T),(4,C),
(5,T)
deadlock

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2 Partner synthesis
Service
?
?€
?C ?T
!B !B
1
2
3 4
5
!€
!C
!T
!€
?B
!C
!T
!€
?B
Petrify: Petri net
oWFN2BPEL: Abstract BPEL
Fact:
this partner
is most
permissive

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3 Partner characterization
Service
?
implemented:
FIONA (OG)
?
?
Why?
-discovery
-substitutability
-test cases
-....
[Petri Nets 07, LNCS ToPNoC II,BPM 08, ACSD 09,IJBPIM 07]

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3 Partner characterization
Service
??
?Provided
Service
Service
Requester
€
C T
Public View
•coin falls
•activate buttons
•evaluate pressed
•heat water
•fill cup

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3 Partner characterization
Service
??
?Provided
Service
Service
Requester
€
C T
Operating
Guidelines
•enter coin
•press button
•take cup

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3 Partner characterization
Service
??
?
?€
?C ?T
!B !B
!€
!C
?B
!€
!T
?B
!T
!€
?B
!C
!€
?B
!€
!C
?B
!T
?B
....
!€
!€ !€
!T
!T !C
!C
?B ?B

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3 Partner characterization
Service
??
?
?€
?C ?T
!B !B
!€
!C
?B
!€
!T
?B
!T
!€
?B
!C
!€
?B
!€
!C
?B
!T
?B
....
!€
!€ !€
!T
!T !C
!C
?B ?B
most
permissive

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3 Partner characterization
Service
??
?
....
!€!€ !€
!T
!T !C
!C
?B ?B
!T∨!€∨!C
!T∨!C

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3 Partner characterization
Service
??
?
....
!€!€ !€
!T
!T !C
!C
?B ?B
!T∨!€∨!C
!T∨!C
!€
!C
?B
!T
?B

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3 Partner characterization
Service
??
?Größe Bedienungsanleitungen
1
10
100
1000
10000
100000
1000000
0 50 100 150 200 250 300 350 400
Knoten PN
KantenOG
Kanten OG

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3 Partner characterization
Service
??
?Berechnungszeit OG
1
10
100
1000
0 50 100 150 200 250 300 350 400
Knoten PN
Zeit(sec)
Zeit

22. Part II

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Substitutability
Service
implemented:
FIONA (deadl. fr.)How?
compare
operating guidelines
Why?
-contracts
Service
?
[DKE 09, CompJ08]

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Transformation
Service
How?
transformation rules
Why?
-contracts
?
[CompJ 08,WWW 08]

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Public View
Service
implemented:
FIONA (deadl. fr.)
How?
re-engineer
operating guideline
Why?
-hide trade secrets
?

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Instance Migration
implemented:
yesWhy?
-long running services
Service
How?
use
operating guidelines
Service
[ICSOC 09]

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Diagnosis
Service
implemented:
yesHow?
inspect garbage in
partner synthesis
[WS-FM 08]

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Repair
Service
implemented:
RACHELHow?
graph based
edit distance
Why?
-suggest (!) correction
Service
[BPM 08]

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Mediation (Adaptation)
Service
implemented:
MarleneHow?
partner synthesis
specification of
semantical constraints
Service
Service
create:
ack: + password: -
copy:
e-mail: + book: -
transform:
mtrsfeet:+ mtrs€:-
...
[submitted]

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partner
Test case generation
implemented:
as hackHow?
select cases from
operating guidelines
of spec
Service
Spec
Service
Impl
partner
partner
Why?
testing without
a partner misses
subtle errors
[WESOA 08, ZEUS 09]

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Realizability
??
Choreography
implemented:
noHow?
decentralized
controllability
[WS-FM 09]

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implicitly covered:
• service discovery
– characterization, matching, public view
• service composition
– compatibility, mediation, partner synthesis, repair
• validation
– controllability, characterization, diagnosis
• n  ∞

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Current Work
• Behavioral Querying
– represent a query by an annotated automaton,
organise registry accordingly
• Other Correctness Criteria
– from deadlock freedom to weak termination
• Split Workflows into Services
• More Problems to Cover

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Problem dimensions
shape of partner
acyclic
centralized
decentralized
autonomus
compatibility notion
deadlock freedom
weak termination
strong termination
covering constraints
messaging
asynchronous
synchronous
queued
semantical constraints other requirements
behavioral constraints
transactions, policies, ...

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Our technology stack
state space exploration ... model checking
partner synthesis ... interaction graph
partner characterization ... operating guideline
inspect / compare / manipulate operating guideline

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Conclusion
• 17+... problems in various settings
• 3+ε powerful technologies
state space, partner synthesis, operating guidelines
• Hype independent through formal modeling
• (8+ Jou, 30+ Conf) publications,
(8+ PhD, 30+ Stud/Dipl) theses, ... since about 2004
• 9+ Cooperations
HU Berlin, TU Eindhoven, Uni Stuttgart, IBM Böblingen+Zürich+Hawthorne Heights, SAP
Brisbane+Walldorf (+Karlsruhe), HPI Potsdam, (Queensland UT), (Uni Tartu)
• 6+ tools
LoLA, Fiona, BPEL2OWFN, OWFN2BPEL, RACHEL, SEDA, ...