A. Dogac Grenoble Ecole de Management MEDFORIST Workshop1 Semantics of Web Services Asuman Dogac...

A. Dogac Grenoble Ecole de Management MEDFORIST Workshop

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Semantics of Web Services

Asuman DogacMiddle East Technical UniversitySoftware R&D CenterAnkara, Türkiye


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Why do we need Web Service Semantics? In order to exploit services in their full potential their properties

must be defined:

The methods of charging and payment The channels by which the service is requested and

provided Constraints on temporal and spatial aspects Availability Service quality Security, trust and rights attached to a service


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Why do we need Web Service Semantics? To be able to describe service properties and later search for services according to

their properties This search needs to be done in a machine

processable and interoperable manner This in turn is possible only by describing the

semantics of Web services through ontology languages


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WSDL does not describe Web service semantics

Web ServiceService Consumer

Web Service Description

defines

Semantic description of the properties of a service in DAML-S

uses


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Taxonomies are not enough to define service semantics:An Example Taxonomy: UNSPSC

43.00.00.00.00Communications and ComputerEquipment and Peripherals and

Components and Supplies

43.16.17.00.00Business Transaction and Personal

Business Software

43.16.17.02.00Tax Preparation Software


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An Example Ontology for Travel Domain

TravelService

EntertainmentService

AccommodationService

ReserveAFlight BuyATicket

AirTransportation

TransportationService


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Properties of ReserveAFlight Generic Service

ReserveAFlight

originatingFrom destinationTo paymentMethod

MyService

How to relate MyService to a generic service class?


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Ontology Languages

Resource Description Framework

DAML+OIL by DARPA and On-To-Knowledge project (European Commission, IST-

1999-10132) Extends RDF with more sophisticated class and property

definitions

OWL (Web Ontology Language) by W3C Based on DAML+OIL

DAML-S by DAML Services Coalition


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Ontology Languages

Have formal specification and thus can be queried

Provide the means to define sophisticated class properties


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DAML-S

describedBy:How it works

Service

ServiceGroundingServiceModel

Resource ServiceProfile

Supports:

How to access it

presents: What it does

provides


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How do we define and use service semantics? There are two key issues:

Where to store the generic semantics of the services

How to associate the ontology classes with the services advertised?


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Where to store the service ontologies? UDDI does not provide an internal

mechanism to store generic service semantics

ebXML, on the other hand, through its classification hierarchy mechanism allows domain specific ontologies to be stored in the registries


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DAML-S ServiceProfile Class

Some of the properties of ServiceProfile class are: parameter property

For example, a subproperty is input, another output serviceParameters, subproperties of which may be

max response time, geographicRadius, … serviceType, high level classification of service such as

B2B or B2C serviceCategory, refers to an ontology of services And more…


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DAML-S

Provides an upper ontology, that is, defines a class called Service

It is necessary to define the lower levels, i.e, domain specific ontologies

Grounding them in upper ontologies like DAML-S makes them more consistent and interoperable

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