Semantic Web Services

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22 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

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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

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, 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





Thank you!