Model-based Methods for Web Service Verification
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Transcript of Model-based Methods for Web Service Verification
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Model-based Methods for Web Service Verification
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Outline
• PAT Introduction and Demo
• Overview of Web Services (WS)– Two views of WS– Problems addressed
• WS Modeling Languages
• WS Verifications
• Experiments
• Conclusion and Future Works
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PAT: Process Analysis ToolkitPAT is a SPIN-like self-contained environment for system specification,
visualized simulation and automated verification.
http://pat.comp.nus.edu.sg
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Two Views of Web Services• Web service choreography describes collaboration protocols of coo
perating Web service participants. – A global point of view– A contract among multiple corporations, i.e., a specification of requireme
nts– May not be executable– WS-CDL (Web Service Choreography Description Language)
• Web service orchestration is the automated arrangement, coordination, and management of (external) Web Services at the message/execution level– A local point of view– An orchestration is the composition of concrete services provided by ea
ch corporation who realizes the contract.– Executable– WS-BPEL (Web Service Business Process Execution Language)
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Problems Addressed
• Verification– Whether a choreography or an orchestration is correct
with respect to critical system properties • Deadlock-freeness• Reachability testing• Temporal logic formulae (LTL)
– Whether they are consistent with each other• the orchestration faithfully implements all and only what the c
ontract states.
• Synthesis– to decide whether a choreography can be realized fait
hfully by any orchestration (refereed as implementable) and
– synthesize a prototype orchestration if possible.
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WS Module Workflow
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WS Modeling Languages
• Intermediate modeling languages for Web services– Languages like WS-CDL or WS-BPEL are designed
for machine consumption and therefore are lengthy and complicated in structure
– Mismatches between WS-CDL and WS-BPEL– Intermediate languages focus on the interactive
behavioral aspect– Our verification and synthesis approaches is not
bound to one particular Web service
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Choreography Language
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Online Shopping Example
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Semantic Model for Choreography
• A system configuration is a 2-tuple (I,V)– I is a choreography and V is a mapping from the varia
bles to their values• Labeled Transition System (LTS) is (S,init,T)
– S is the set of reachable configurations, – init is the initial state (i.e., the initial choreography and
the initial valuation of the variables) and – T is a labeled transition relation defined by the semant
ics rules.– Transition– Execution– Single Trace– Traces
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Orchestration Language
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Online Shopping Example
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Verifications
• Deadlock-freeness• Reachability testing• Temporal logic formulae (LTL)• Conformance Checking
– An orchestration O is valid implementation of a choreography I if and only if O refines I, i.e., traces(O) ⊆ traces(I)
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Conformance Checking Algorithm
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Experiments
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Conclusion
• A model-based methods for fully automatic analysis of Web service compositions – Intermediate languages– Verification– Synthesis (light-weight)
• Future Works– Language enrichment
• Event handlers, fault handlers and compensation handlers. – To support more Web service composition language, e.g., Orc
language. – Automatic conversions between WS-BPEL/WS-CDL and our
language– Optimization techniques
• Candidates include those which are designed for parameterized systems and infinite state systems