A Logical Framework for Web Service Discovery

1. A Logical Framework for Web Service Discovery The Third International Semantic Web Conference Hiroshima, Japan, 08-11-2004 Michael Kifer1, Rubén Lara2, Axel Polleres2, Chang Zhao1, Uwe Keller2, Holger Lausen2, and Dieter Fensel2 ruben.lara@deri.org 1Department of Computer Science University at Stony Brook, New York, USA 2Digital Enterprise Research Institute, Innsbruck, Austria, and Galway, Ireland

2. Overview • Introduction • Proof obligations and formalization • Realization • Semantics of rule reification • Conclusions & future work Rubén Lara ruben.lara@deri.org

3. Automatic discovery • Current Web Services have to be selected and hard-wired at design time • No dynamic reconfiguration of services • Semantics can enable the automatic location of Web Services providing particular functionality Rubén Lara ruben.lara@deri.org

4. WSMO & WSML Objectives that a client may have when consulting a Web Service Semantic description of Web Services: • Capability • Interfaces Provide the formally specified terminology used by all other components Connectors between components to bypass heterogeneity F-Logic + Transaction Logic Rubén Lara ruben.lara@deri.org

5. The problem • Matching capabilities of existing Web Services against the goal described by the requester • Consideration of the functionality of the Web Service • Distinction between discovery and contracting • Example implementation using Rubén Lara ruben.lara@deri.org

6. Overview • Introduction • Proof obligations and formalization • Realization • Semantics of rule reification • Conclusions & future work Rubén Lara ruben.lara@deri.org

7. Goals, capabilities & mediators • Goal describes (in terms of domain ontologies) the desired state of: • Information space • State of the world • Web Service capabilities describe (in terms of domain ontologies): • What the service expects to provide its functionality • What is guaranteed to hold after execution • wgMediators link Web Services and goals, resolving heterogeneity • Resolve possible terminology differences Rubén Lara ruben.lara@deri.org

8. Logics and scalability issues • Logic can be used to formalize goals, capabilities and proof obligations • Scalable framework must rely on a relatively small number of logicians • Mediation Provider: • - Bulk of logical expertise • Link ontologies, not customers and providers • Service Provider: • - modest requirements • Capabilities written to relatively simple ontologies • Relatively simple types of rules • Customer: • - no training in KR • pre-defined discovery queries • goal ontology Rubén Lara ruben.lara@deri.org

9. Proof obligations (I) • Set of imported ontologies O • GoalG • Service capability C (Ceff and Cpre) • wgMediator wg • takes a goal G and constructs input Inwg(G)suitable for services mediated • Converts the goal into a postcondition Postwg(G)expressed in terms of the service ontology • Mediation can be complex: • Goals can be expressed in a very high level syntax • Service capabilities can be rather simple Rubén Lara ruben.lara@deri.org

10. Proof obligations (II) • Service discovery • Given a goal G, can the service execute in a way such that G can be achieved? • Service contracting • Given an actual input to a specific service, does this input lead to the results expected by the requester? Rubén Lara ruben.lara@deri.org

11. Proof obligations (III) • Proof obligations before • Deal with a particular service • Different services have different effects • Use of transaction logic • is the sequence operator • is the hypothetical operator Rubén Lara ruben.lara@deri.org

12. Overview • Introduction • Proof obligations and formalization • Realization • Semantics of rule reification • Conclusions & future work Rubén Lara ruben.lara@deri.org

13. Realization • Use of : • Support for F-Logic, HiLog, Transaction Logic and rule reification • Geographic ontology Rubén Lara ruben.lara@deri.org

14. Realization (II) • Goal ontology: • Service1: Conditions over the input Input is a search -> provide itinerary wgMediator used Rubén Lara ruben.lara@deri.org

15. Realization (III) • Service 3: • Goals: Uses goal ontology Region! Rubén Lara ruben.lara@deri.org

16. Realization (IV) • Mediator: Takes the goal and constructs input to the service Takes the result and checks it according to the format specified in the goal Rubén Lara ruben.lara@deri.org

17. Realization • Discovery Construct input Generate effects Assume effects Check goal Remove effects Rubén Lara ruben.lara@deri.org

18. Overview • Introduction • Proof obligations and formalization • Realization • Semantics of rule reification • Conclusions & future work Rubén Lara ruben.lara@deri.org

19. Semantics of rule reification • Model theory for F-Logic extended with rule reification defined • Reified F-Logic avoids paradoxes through two restrictions: • No negation is allowed in the rule head, and • Reification of negation of any fact or any rule is not permitted Rubén Lara ruben.lara@deri.org

20. Overview • Introduction • Proof obligations and formalization • Realization • Semantics of rule reification • Conclusions & future work Rubén Lara ruben.lara@deri.org

21. Conclusions • Logical framework and realization for: • dynamic discovery of Web Services • verification of contractual statements • Scalable framework in terms of human resources by exploiting mediators • The framework captures the relation between inputs and effects, thus providing more accurate descriptions and discovery • Easily extendable to include invocation Rubén Lara ruben.lara@deri.org

22. Future work • In progress • Alignment with WSML • Integration with other types of web service discovery • Further investigation on border between ggMediation and wgMediation • Complete knowledge goals in the absence of sufficient domain knowledge • Implementation of WSMO discovery engine • Planned • Integration with composition Rubén Lara ruben.lara@deri.org

23. Conclusions </A Logical Framework for Web Service Discovery> <Q&A> Rubén Lara ruben.lara@deri.org