Agent Model for Interaction with Semantic Web Services Ivo Mihailovic

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

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

Semantic Web

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).

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.

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

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

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

OWL-S

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.

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

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

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

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

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.

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

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

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

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

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

Service composition AI planning to form service composition A planning problem P is a 3-tuple 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.

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

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

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