Agent Model for Interaction with Semantic Web Services

1. Agent Model for Interaction with Semantic Web Services Ivo Mihailovic

2. Overview • Introduction • About Semantic Web • About Web Services • About Semantic Web Services • The model of the agent • eGovernment example

3. Introduction • An attempt to demystify the Semantic Web to the author • Agent for interaction with Semantic Web Services • Integration of eGov services: providing a single access point to all government services, the increase in their interoperability without affecting their autonomy, approach oriented towards citizens

4. Semantic Web

5. Web Services • The W3C defines a Web service as a software system designed to support interoperable Machine to Machine interaction over a network. • Require three basic components: A messaging service for communicating between resources on the Web (SOAP), An interface description language (WSDL), A registration service so that clients looking for a service can find them (UDDI).

6. Semantic Web Services • Semantic Web Services are self-describing, semantically marked-up software resources that can be interacted with in a task driven automatic way. • Dynamic part of the semantic web.

7. Semantic Web Services • Automated Web Service Discovery • Automated Web Service Invocation • Automated Web Service Composition • Automated Web Service Monitoring • Automated Web Service Verification • Automated Web Service Simulation

8. Semantic Web Services • WSDL can specify the operations available through a web service and the structure of data • WSDL cannot specify semantic meaning of the data or semantic constraints on the data. • WSMO vs OWL-S

9. WSMO

10. WSMO • Ontologies – describe all relevant concepts and relations among them • Web Services - describe capabilities, interfaces and internal working of the Web service • Goals - describe the capability the user would like to have and the interface he would like to interact with • Mediators - define mappings between components

11. OWL-S

12. OWL-S Service Profile • Service Profile – describes what the service does, used for the discovery • Intended to be published in a WS registry • Classification through the creation of a subclass hierarchy (one WS can belong to multiple classes) • IOPEs represent Web service’s capabilities, they describe the service • Other features: contact information, category, quality rating etc.

13. OWL-S Process Model • Process Model – describes how the service works, its operation, control and data flow • Used for selection, invocation, interoperation, composition, and monitoring of the WS • Process types: atomic, simple, composite

14. OWL-S Grounding • Grounding specifies how to access the service in terms of communication protocols and message descriptions • Mapping from Process Model to WSDL

15. Agent model • Example: The user wants to book a flight. • He should find a service that sells tickets, check if it accepts his credit card and book the flight • The agent can automate this using an ontology of Web services • Agent tries to resolve the semantics of the user with the semantics of the service • User provide goals, agent try to map them to actions

16. Agent model • Example: Goal – to go on a business trip. Actions – to book a flight, a taxi to the hotel and a hotel room • Example: Goal – the change of address. • Agent needs two ontologies: • First to map user’s requests to available goals • Second to map goals to Web services

17. Scenario of operation • Step 1) User enters the query • Step 2) Agent maps user’s requirements to goals • The hard part – needs NLP, needs to be able to interpret user’s constraints • Book me a flight if the weather’s nice.

18. Scenario of operation • Step 3) Agent tries to discover a service for each goal • Step 4) If it cannot find an integrated service for a goal it tries to decompose it • Step 5) After making the plan of actions the agent invokes the services

19. Area of application: e-Gov • Integration of services, increased interoperability, not affection the autonomy of government organizations • Government is a dynamic area, things constantly changing (especially in countries in transition) • Services easily changed, added or removed

20. Area of application: e-Gov • E-Government Domain Ontology encodes organizational, legal, economic, business etc. concepts • Web services ontology should categorize services to enable discovery • Registry of Web services with the service descriptions • A change of the service requires the update of the description

21. Service discovery • WSMO – comparing Goals to Web Service descriptions • OWL-S – using the Service Profile • Service classification by creating a hierarchy of subclasses of Service Profile • SWS yellow pages – a class-hierarchical taxonomy

22. Service discovery • Classification by serviceProduct and serviceCategory properties • Mapping to an OWL specification of UNSPSC (United Nations Standard Products and Services Code) • Also can be connected to a classification outside of OWL

23. Service composition • AI planning to form service composition • A planning problem P is a 3-tuple < I, G, A > • I – description of the initial state • G – description of the goal state • A – set of actions for state transformations • An action sequence (a plan) S is a solution to P if S can be executed from I and the resulting state of the world contains G.

24. Service composition • States formed from user’s goals and services preconditions and results • Actions are descriptions of Web services which show how their execution modifies the state of the world • STRIPS algorithm

25. E-Gov ontology • Needs to represent the viewpoint of citizens as well as government • Connecting terms from common language with their legal jargon counterparts • Descriptions of non web-based services as well • Planner could make hybrid composition

26. Thank you!