A Feature-Complete Petri Net Semantics for WS-BPEL 2.0
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This document describes a Petri net semantics for the WS-BPEL specification. It presents a formal model of open workflow nets to represent WS-BPEL processes. This semantics maps WS-BPEL activities like receive, flow, and scope to patterns in open workflow nets. The semantics allows formal analysis of WS-BPEL processes and has been implemented in a tool that converts BPEL processes to Petri nets.
A Feature-Complete Petri Net Semantics for WS-BPEL 2.0
- 2. WS-BPEL A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 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> 2
- 3. Petri Net Semantics for WS-BPEL A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 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 3
- 4. Example: <receive> Activity initial A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 stop t4 channel x t1 x running x t5 x x x variable v t2 y stopped t3 faulted t6 faultName t7 failed final 4
- 5. Example: <flow> Activity A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 initial stop t1 t3 running t4 A B t5 sync stopped t6 final 5
- 6. New Features of WS-BPEL 2.0 A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 Semanticclarifications What happens during compensation? Syntactic sugar <repeatUntil> activity, inline validation, … Some new activities and features <forEach> activity, termination handlers, ... 6
- 7. Implementation A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 BPEL2oWFN meta model Petri net model Abstract Petri Net Syntax Tree API BPEL process Petri net Control/Data Pattern Input Formats: Flow Graph Repository Output Formats: WS-BPEL 2.0 Fiona oWFN static analysis pattern selection BPEL4WS 1.1 LoLA Abstract WS-BPEL 2.0 PNML BPEL4Chor INA, PEP, SPIN WSDL 1.1 … http://www.gnu.org/software/bpel2owfn 7
- 8. Applications of the Semantics (1) A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 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 8
- 9. Tools4BPEL Tool Chain (1) A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 BPEL2oWFN WS-BPEL Petri Net Process Model LoLA2BPEL LoLA Witness Path 9
- 10. Applications of the Semantics (2) A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 Open workflow nets allow for… Analysis of the open workflow net Consistency Controllability Partner synthesis … Synthesis results can be re-translated to WS-BPEL 10
- 11. Tools4BPEL Tool Chain (2) A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 BPEL2oWFN WS-BPEL oWFN Process Model oWFN2BPEL Fiona Partner oWFN 11
- 12. Summary (1) A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 Feature-complete semantics for WS-BPEL 2.0 and its predecessor specification Simplified patterns for important constructs Case study: Old Semantics New Semantics Places 410 242 Transitions 1,069 397 States 6,261,648 304,007 Compiler BPEL2oWFN 12
- 13. Summary (2) A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 Petri net semantics allows to formally analyze WS-BPEL processes Analysis results can be re-translated into WS-BPEL Completetool chains help to “conceal” formal methods from the WS-BPEL designer Danger: new semantics needed for future versions WS-BPEL 2.1, WS-BPEL 3.0, WS-BPEL 4.0, … Thank you very much! 13
- 15. Parallel <forEach> A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 initial initialize running stop1 initial stop stop stop3 x b stop2 stopped active stopping t1 stopped scope Successful x=0 skipping all stopped x t2 x !Successful x=0 c x-1 counter finish2 t3 x final x>0 t4 finish1 done instance 1 final 15
- 16. <scope> A Feature-Complete Petri Net Semantics for WS-BPEL 2.0 !Exiting Exiting initial fault in ch fault up compensate Active fn fn inner stopped fn fn ignore fault !Active initialize Active term Successful !Successful Active !Active pass handle fn !Active start ch skip ch start th skip th inner fsave stopped stop stop stop ch stop stop inner activity inner activity of the stopped skip ch stopped termination stopped and stopped fault handlers compensation handler event handlers handler stopped fault in fault up fn fault up ch fault up final compensated stopped finalize fn fn !Successful Successful final ch fault in compensated positive control flow fault handling compensation handling termination handling 16