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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
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 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, 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.
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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