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DecSerFlow Towards a Truly Declarative
Service Flow Language
Wil van der Aalst & Maja PesicEindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
Invited talk 3rd International Workshop onWeb Services and Formal Methods8 September 2006, Vienna, Austria
Outline
1. Classical approaches• BPEL2PN• PN2BPEL
2. DecSerFlow• Language• Graphical notation and LTL semantics• Implementation and application
(specification and enactment)
3. Using DecSerFlow for process mining
4. Conclusion
Classical approaches
BPEL2PN
PN2BPEL
1. Formal languages (Petri nets, LTS, YAWL)
2. Graphical languages(BPMN,UML-AD)
Industry standards:1. BPEL2. (abstract) BPEL3. WS-CDL4. etc.
BPEL2PN• Many translations are available, cf.
– S. Hinz, K. Schmidt, and C. Stahl. Transforming BPEL to Petri nets. BPM 2005.
– C. Stahl. A Petri net semantics for BPEL. Technical Report 188, Humboldt Universität zu Berlin, June 2005.
– etc.– C. Ouyang, W.M.P. van der Aalst, S. Breutel, M. Dumas, A.H.M. ter
Hofstede, and H.M.W. Verbeek. Formal semantics and analysis of control flow in WS-BPEL. Technical Report BPM-05-13, BPMcenter.org, June 2005.
• Focus on analysis, i.e., verification of various properties.• Our approach is implemented in BPEL2PNML and
WofBPEL.• cf. BEST (Berlin-Eindhoven Service Technology)
program also involving tools such as BPEL2PN, LOLA and FIONA
Example
Corresponding Petri net
PN2BPEL
• Joint work with Kristian Bisgaard Lassen.• Few people have been working on this.• Purpose: Generating readable BPEL code
(otherwise it has no purpose).• Implemented in WorkflowNet2BPEL4WS and
ProM.• Not complete, but extendible.• Work with Chun Ouyang, Marlon Dumas, et al.
(QUT) on using concepts in context of BPMN.
Basic idea
• Discover WF-net like components.
• Look for specific patterns that can easily be mapped onto BPEL (sequence, pick, switch, while, flow, etc.).
• Allow for ad-hoc extensions and re-use these.
4 types: PP, TP, PT, and TT components
Sequence
Flow
•acyclic•explicit choice•well-structured
Example
Fold sequence
Fold switch
Fold sequence
Fold sequence (2x) and pick (2x)
Final step: fold flow
Tool support: WorkflowNet2BPEL4WS and ProM
Empirical case study: 100 Protos• Different student projects.• Size of models: 23.66 places and 26.54 transitions.
• Reductions:
DecSerFlowTowards a Truly Declarative
Service Flow Language
joint work with Maja Pesic (TU/e)
Problems
• Tendency to over-specify.
• Focus on execution rather than "contractual" side.
Proposal• A more declarative approach
– Graphical– Executable– Analysis support (both design and run-time)
Basic idea
A B
DecSerFlow notation LTL semantics
LTL
Small example
1. Existence formulas
0
A
2..*
A
3..*
A
N..*
A
0..2
A
0..N
A
0..1
A
2
A
N
A
1
A
N..*
A
0..N
A
N
A
A
1..*
2. Relation formulas
A B
A B
A B
A B
A B
A B
A B
A B
A B
A B
A B
Example: "existence response"
• OK:– [ ]– [A,B,C,D,E]– [A,A,A,C,D,E,B,B,B]– [B,B,A,A,C,D,E]– [B,C,D,E]
• NOK– [A]– [A,A,C,D,E]
A B
Example: "response"
• OK:– [ ]– [A,B,C,D,E]– [A,A,A,B,C,D,E]– [B,B,A,A,B,C,D,E]– [B,C,D,E]
• NOK– [A]– [B,B,B,B,A,A]
A B
Example: "precedence"
• OK:– [ ]– [A,B,C,D,E]– [A,A,A,C,D,E,B,B,B]– [A,A,C,D,E]
• NOK– [B]– [B,A,C,D,E]
A B
Combinations
A B A BA Band =
A B A B A Band =
co-existence
succession
3. Negation formulas
A B
A B
A B
A B
A B
A B
A B
A B
A B
A B A B
Example: "neg succession"
• Not the logical negation!• OK:
– [ ]– [A,C,D,E]– [A,A,A,C,D,E]– [B,B,A,A,C,D,E]– [B,C,D,E]
• NOK– [A,B]– [B,A,A,C,D,E,B]
A B
A B
A B A B
or
Using DecSerFlow
• Nature of model:– Global model (choreography model), i.e., interactions are
described from the viewpoint of an external observer who oversees all interactions between all services (non-executable specification of a contractual nature).
– Local model, i.e., the DecSerFlow model is used to specify, implement, or configure a particular service.
• Use:– Analysis of both global and local models.– Comparing global and local models.– Monitoring global and local models (conformance).– Enactment of local models.
Enactment
• A Büchi automaton typically assumes traces infinitely visiting an accepting state. There are several ways to address this. We use the approach proposed by Dimitra Giannakopoulou and Klaus Havelund to check finite traces.
• We can color the constraints green (in accepting state), yellow (accepting state can still be reached), or red (accepting state cannot be reached anymore).
Implementation (ConDec)
• Implementation on top of YAWL and ProM.• Editor (with facilities to extend language) has been
implemented.• Initial experiments with enactment service.• Plans to link editor with LTL checker in ProM.
YAWL
Prom
interface B
Editor
Add your own constraints!
Using DecSerFlow for process mining
curse prayresponse
Thanks to Ton Weijters, Boudewijn van Dongen, Ana Karla Alves de Medeiros, Anne Rozinat, Christian Günter, Eric Verbeek, Ronny Mans, Minseok Song, Laura Maruster, Huub de Beer, Peter van den Brand, Jan Mendling, Andriy Nikolov, Jianmin Wang, Lijie Wen,
Irene Vanderfeesten, Mariska Netjes, Steffi Rinderle, Walid Gaaloul, Gianluigi Greco, Antonella Guzzo, Maja Pesic, etc. etc.
Overview: Process mining
web servicesservice flow
processmodel
eventlogs
specifies global model
discovery
records events, e.g.,
via SOAP messages
specifies/implements local model
supports/controls
extension
conformance
Discovery
• Based on an event log a model is constructed without a-priori information.
• Not just the control-flow, cf. the social network miner.
• ProM examples: alpha algorithm, heuristics miner, multi-phase miner, genetic miner, etc.
web servicesservice flow
processmodel
eventlogs
specifies global model
discovery
records events, e.g.,
via SOAP messages
specifies/implements local model
supports/controls
extension
conformance
DecSerFlow
Alpha miner
Other examples
Export to CPN Tools, PNML, ARIS, EPC Tools, YAWL, Netminer, etc.
Conformance
• The log is compare with some a-priori model, the model can be a Petri net, EPC, data model, logical/temporal property, etc.
• ProM examples: conformance checker and LTL checker
web servicesservice flow
processmodel
eventlogs
specifies global model
discovery
records events, e.g.,
via SOAP messages
specifies/implements local model
supports/controls
extension
conformance
DecSerFlow
Examples
Extension
• An existing model is enriched with additional knowledge extracted from log.
• ProM examples: decision miner, staff assignment miner, performance analyzer, etc.
web servicesservice flow
processmodel
eventlogs
specifies global model
discovery
records events, e.g.,
via SOAP messages
specifies/implements local model
supports/controls
extension
conformanceDecSerFlow
Examples
Export to CPN Tools!
Conformancein webservices in a classical setting(abstract BPEL + SOAP messages)
<receive …createInstance=”YES”><correlations/></receive>
<invoke …inputVariable = …outputVariable = ...><correlations/></invoke>
<invoke …inputVariable = … ><correlations/></invoke>
<receive …variable = … ><correlations/></receive>
(MT,PI)
<reply … >variable = …</receive>
abst
ract
BP
EL
SO
AP
Mes
sage
s
SO
AP
Mon
itor/
Cor
rela
tor
(MT,PI)(MT,PI)(MT,PI)(MT,PI)(MT,PI)
...
Event log
A
E
G
D
H I
J
K
M
L
C
B
G
F
(MT,PI)
(MT,PI)
(MT,PI)
Petri net
Conformance checking!
Info
rmat
ion
Sys
tem
Conformance?
Conclusion
• Classical approaches:– BPEL2PN: mainly for analysis purposes. – PN2BPEL: also as an example for BPMN2BPEL, etc.
• DecSerFlow– Graphical notation, LTL semantics, extendible.– Linked to YAWL and ProM.
• Similar to ConDec aiming at supporting autonomous (groups of) workers.
• Interesting links between groupwork and services.
Relevant WWW sites
• http://www.processmining.org
• http:// promimport.sourceforge.net
• http://prom.sourceforge.net
• http://www.workflowpatterns.com
• http://www.workflowcourse.com
• http://is.tm.tue.nl/
• http://is.tm.tue.nl/staff/wvdaalst