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Slides prepared by Marcus Venzke

Formal Specification Of Web Services For Dependable Systems contribution to the PISA Workshop (25. – 27. 11. 2002) on the IP DeSIRE and the NoE DeFINE Prof. Dr. F. VOGT TELEMATIK TU Hamburg-Harburg. Slides prepared by Marcus Venzke. WSDL is Not Enough!. Interface = Contract!

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Slides prepared by Marcus Venzke

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  1. Formal Specification Of Web Services For Dependable Systemscontribution to the PISA Workshop(25. – 27. 11. 2002)on the IP DeSIRE and the NoE DeFINEProf. Dr. F. VOGTTELEMATIKTU Hamburg-Harburg Slides prepared by Marcus Venzke

  2. WSDL is Not Enough! Interface = Contract! Described in WSDL Is part of Contract!

  3. Describing Relations • Relations expressed in predicate logic • Required: Operations to handle XML!(For expressions about SOAP messages.) • To be described: • SOAP body • SOAP header entries • SOAP error messages (E.g.: When is which returned?) • Description of dynamic behavior • E.g. Allowed order of operation calls • Relation between SOAP message and history (Can be expressed in predicate logic.) • Similar to: Hoare‘s Traces(See: Hoare, C.A.R: Communicating Sequential Processes. Prentice-Hall International, UK, LTD, 1985.) Also relations among each other!

  4. Predicate Logic Expressions in WSDL • WSDL + Description of relations= Complete description of contract • Advantage: Contract completely in WSDL document • Extensions allowed in WSDL (as „extensibility elements“) • Predicate logic expressions can be put there • Goals of extended WSDL: • Documentation for developers • Basis for automatic validation und verification

  5. Automatic Validation Validator: Checks for every message, if it conforms to the specification. • Automatic validation: • To be checked: • Message a valid SOAP message?(Conforming to SOAP standard) • SOAP message conforming to „classic WSDL“? • Includes XML Schema validation • Are all predicate logic expressions true?

  6. Verification of Web Services • Formal specification of interface = Basis for verification • To be considered: • Predicate logic expressions • Everything described in WDSL • including parts in XML Schema • Implicit things from SOAP standard • Advisable (if possible): Transformation of WSDL und implicit things into predicate logic expressions. Must not be forgotten!

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