1. SEERC - Research Centre of the University of Sheffield and CITY College 1 Leveraging Semantic Web Service Descriptions for Validation by Automated Functional Testing Ervin Ramollari 1, Dimitrios Kourtesis 1, Dimitris Dranidis 2, and Anthony Simons 3 1 SEERC – South East European Research Centre 2 Computer Science Department – CITY College 3 Department of Computer Science – University of Sheffield

2. SEERC - Research Centre of the University of Sheffield and CITY College 2 Presentation outline 1.Background and motivation 2.The starting point: semantic descriptions of Web service behaviour 3.The destination: Stream X-Machine model of Web service behaviour 4.The derivation method: from IOPE descriptions to an SXM model 5.Test case generation and execution 6.Summary and future work

3. SEERC - Research Centre of the University of Sheffield and CITY College 3 Background and motivation

4. SEERC - Research Centre of the University of Sheffield and CITY College 4 Testing and validation of Web services A service-oriented environment can be open  Integration of third-party Web services  Dependability is a major challenge Service validation is crucial for engineering dependable service-based systems  Web service implementation should conform to given functional/behavioural specifications  Validation done through functional testing Manual Web service testing is highly laborious  Definition of test cases, execution and evaluation

5. SEERC - Research Centre of the University of Sheffield and CITY College 5 Leveraging SWS descriptions for automating testing Semantic Web Service descriptions are utilised for automating a range of activities  Service discovery, composition, mediation… Less attention has been paid to using them for service testing and validation Information in SWS descriptions could be exploited for automating test case generation and execution This information should be represented in a formalism amenable to processing by existing algorithms and tools for test case generation and execution

6. SEERC - Research Centre of the University of Sheffield and CITY College 6 Our background work Functional testing of Web services  Automated generation and execution of test cases (with completeness guarantees) Stream X-Machine (SXM) formalism  Used for modelling the behaviour of stateful and conversational Web services  Associated with proven testing method revealing all inconsistencies between implementation and model Tool support  SXM modelling, model animation, test case generation, test case execution on WS

7. SEERC - Research Centre of the University of Sheffield and CITY College 7 Aim of this work Could we derive a SXM model from a Semantic Web Service description for the purposes of automated testing and validation? The derivation approach should be:  Automatable to the greatest extent possible  Independent of any particular SWS framework  Using Semantic Web technology standards

8. SEERC - Research Centre of the University of Sheffield and CITY College 8 The starting point: semantic descriptions of Web service behaviour

9. SEERC - Research Centre of the University of Sheffield and CITY College 9 Semantic descriptions of Web service behaviour SWS frameworks like OWL-S, WSMO (and ad- hoc SA-WSDL combinations) are heterogeneous A commonality is describing service operations in terms of inputs, outputs, preconditions, and effects (IOPE)  Transformation of inputs to outputs  Conditional effects on the internal state All SWS frameworks support IOPE in some form  OWL-S: Inputs, Outputs, Preconditions, Results  WSMO: Preconditions, Postconditions, Assumptions, Effects  SAWSDL: ModelReference annotations on operations

10. SEERC - Research Centre of the University of Sheffield and CITY College 10 IOPE-based descriptions IOPE is useful for describing stateful and conversational Web services  E.g. shopping cart, e-banking, order management… IOPE representation requires a combination of  Production rules for expressing:  Conditions for execution (preconditions)  Actions of execution (effects in terms of assertions and retractions)  Ontology for expressing:  Structure of inputs and outputs  Internal state-related variables (i.e. not visible in WSDL)

11. SEERC - Research Centre of the University of Sheffield and CITY College 11 IOPE-based descriptions with RIF-PRD + OWL In this paper we adopt RIF-PRD and OWL as a possible combination Why RIF-PRD?  RIF as rule language for the Semantic Web  Production Rule Dialect has operational semantics (specified as an LTS)  RIF-PRD forthcoming W3C recommendation Why OWL?  W3C recommendation

12. SEERC - Research Centre of the University of Sheffield and CITY College 12 The destination: Stream X-machine model of Web service behaviour

13. SEERC - Research Centre of the University of Sheffield and CITY College 13 Stream X-machines Stream X-Machines, specialisation of the X-machine model (Eilenberg 1974)  8-tuple (Σ, Γ, Q, M, Φ, F, q 0, m 0 )  Extend Finite State Machines (FSM) with:  Memory  Processing functions labelling transitions  Complete functional testing method  Proven to reveal all faults in an implementation given that certain design for test conditions are satisfied

14. SEERC - Research Centre of the University of Sheffield and CITY College 14 Bank account service example Service operations  open  deposit  withdraw  getBalance  close Operations are invoked according to a protocol (choreography)

15. SEERC - Research Centre of the University of Sheffield and CITY College 15 Bank account service SXM Model

16. SEERC - Research Centre of the University of Sheffield and CITY College 16 SXM processing functions for operation withdraw withdraw.amount > 0 && balance > withdraw.amount balance = balance - withdraw.amount; withdrawOut.amount = withdraw.amount; withdraw.amount > 0 && balance == withdraw.amount balance = balance - withdraw.amount; withdrawOut.amount = withdraw.amount;

17. SEERC - Research Centre of the University of Sheffield and CITY College 17 The derivation method: from IOPE descriptions to an SXM model

18. SEERC - Research Centre of the University of Sheffield and CITY College 18 Identifying state variables (* wsdl:operation withdraw *) Forall ?account ?status ?balance ?request ?withdrawAmount ( And ( ?account#Account ?account[hasStatus->?status] ?account[hasBalance->?balance] ?request#WithdrawRequest ?request[hasAmount->?withdrawAmount] ) If And (External (pred:string-equal(?status "ACTIVE") External (pred:numeric-greater-than-or-equal(?balance ?withdrawAmount) ) Then Do(Retract (?account[hasBalance->?balance]) Assert(?account[hasBalance->External(func:numeric- subtract(?balance ?withdrawAmount))]) Retract (?request) (?response New(?response#WithdrawResponse)) (?newBalance ?account[hasBalance->?newBalance]) Assert (?response[hasAmount->?newBalance) ) ) Two state variables:  hasBalance  hasStatus

19. SEERC - Research Centre of the University of Sheffield and CITY College 19 Partition analysis The domains of state variables are determined by consulting their respective ranges in the OWL ontology. hasBalance :== 0…∞ hasStatus :== {INITIAL, ACTIVE, CLOSED}

20. SEERC - Research Centre of the University of Sheffield and CITY College 20 Partition analysis State :== hasStatus x hasBalance  E.g. (INITIAL, 0), (INITIAL, 1), …, (ACTIVE, 0), (ACTIVE, 1), … Examine the preconditions to partition ranges of state variables If And ( External (pred:string-equal(?status "ACTIVE") External (pred:numeric-greater-than-or- equal(?balance ?withdrawAmount) )  hasStatus:  ?status = INITIAL  ?status = ACTIVE  hasBalance:  ?balance = 0  ?balance ≥ ?withdrawAmount AND ?withdrawAmount > 0 Result  hasStatus: {INITIAL}, {ACTIVE}, {CLOSED}  hasBalance: {0}, {x | x>0}

21. SEERC - Research Centre of the University of Sheffield and CITY College 21 Identifying preliminary states The preliminary state space is defined as the product of the state variable partitions. Six states

22. SEERC - Research Centre of the University of Sheffield and CITY College 22 Determining transition pre-states An input is accepted at a state (pre-state) iff the preconditions are satisfied at the pre-state E.g. the preconditions of the withdraw operation triggered WithdrawRequest are (hasStatus=ACTIVE and hasBalance>0).

23. SEERC - Research Centre of the University of Sheffield and CITY College 23 Merging states Preliminary states in which the same set of inputs is accepted are merged  Cannot be distinguished

24. SEERC - Research Centre of the University of Sheffield and CITY College 24 Determining transition post-states Apply the effects of the invoked operation on the pre-state to determine the possible post-states. WithdrawRequest leads to two possible post- states  Two different transitions labelled by different processing functions Isolated states are removed.

25. SEERC - Research Centre of the University of Sheffield and CITY College 25 Determining guard conditions for processing functions The guard conditions are the same as the corresponding rule preconditions Any predicates already satisfied in the pre- state are omitted.

26. SEERC - Research Centre of the University of Sheffield and CITY College 26 Determining memory updates for processing functions The memory updates of each processing function consist only of the effects which update the memory (M) variables.

27. SEERC - Research Centre of the University of Sheffield and CITY College 27 Test case generation and execution

28. SEERC - Research Centre of the University of Sheffield and CITY College 28 Generation of test cases SXM test generation based on Chow’s W- method for FSMs X = S(Φ k+1 U Φ k U … U Φ U {})W, where  Φ is the set of processing functions (type of the machine)  W is the characterisation set  S is the state cover  k is an estimate of maximum path length between redundant states in the implementation Supported by tools

29. SEERC - Research Centre of the University of Sheffield and CITY College 29 From abstract to concrete test cases The generated test cases are at the same level of abstraction as the specification and cannot be executed directly Abstract test cases are transformed to JUnit test cases Generation of Java clients with libraries such as WSDL2Java Value of kNo. of test sequencesExecution time k=0253.9 s k=17211.5 s k=223045.2 s

30. SEERC - Research Centre of the University of Sheffield and CITY College 30 Execution of Test Cases

31. SEERC - Research Centre of the University of Sheffield and CITY College 31 Summary and future work

32. SEERC - Research Centre of the University of Sheffield and CITY College 32 Summary of the approach Leveraging SWS descriptions for the added-value of testing and validation of services Strengths of the approach:  SWS framework-independent  Testing supported by existing tools  Uses proven SXM functional testing method

33. SEERC - Research Centre of the University of Sheffield and CITY College 33 Related work Sinha and Paradkar 2006  OWL and SWRL rules to describe IOPE  Single-state EFSM  No prescribed test generation method Keum et al. 2006  Derive multi-state EFSM from plain WSDL + user-supplied information  Only derivation of states is described

34. SEERC - Research Centre of the University of Sheffield and CITY College 34 Future work Investigate the decidability of the algorithm and the automation of all steps Implement tools supporting the transformation Prove equivalence relationship among original specification and derived SXM model Utilise SWS grounding information to automate the transformation of abstract test cases to concrete (SA-WSDL annotations pointing to RIF- PRD and OWL)

35. SEERC - Research Centre of the University of Sheffield and CITY College 35 Thank you for your attention!