Semantic Web Services Peter Bartalos Dr Jorge Cardoso

Semantic Web Services Peter Bartalos

Dr. Jorge Cardoso and Dr. Amit Sheth http: //dme. uma. pt/jcardoso/Books/Semantic-Web-Services-Processes-and-Applications/ 2

Semantic Web o o Machine understandable Web content Not a separate Web but an extension (semantic) meta-data RDF, OWL 3

Web Service “A Web service is a software system identified by a URI, whose public interfaces and bindings are defined and described using XML. Its definition can be discovered by other software systems. These systems may then interact with the Web service in a manner prescribed by its definition, using XML based messages conveyed by Internet protocols" 4

Web Service “A Web service is a software system identified by a URI, whose public interfaces and bindings are defined and described using XML. Its definition can be discovered by other software systems. These systems may then interact with the Web service in a manner prescribed by its definition, using XML based messages conveyed by Internet protocols" 5

Semantic Web services o Semantic Web services are the result of the evolution of the syntactic definition of Web services and the semantic Web Bussler et al 2003: A Conceptual Architecture for Semantic Web Enabled Web Services 6

Semantic Web services o Web services are: n n o Modular Self-describing Self-contained Accessible over the Internet Described using WSDL n n WSDL - Web Services Description Language Provide operational information Does not contain semantic descriptions It specifies the structure of message components using XML Schema constructs 7

Semantic Web services o Solution: n Mapping concepts in a Web service description to ontological concepts OWL-S, WSMO, SWSF, WSDL-S, SAWSDL 8

Semantic Web services o Submissions to the W 3 C: n n n OWL-S WSMO WSDL-S OWL-S, WSMO, SWSF, WSDL-S, SAWSDL 9

Semantic Web service discovery o o o Discovery n The procedure of finding a set of appropriate Web services Problem n How to efficiently discover Web services Currently n Universal Description Discovery and Integration (UDDI) n Relatively inefficient n Does not take into account the semantics of Web services Web Service Discovery, Verma et al 2003: MWSDI Downloadable Tool: Lumina - Semantic Web Service Discovery 10

Semantic Web service discovery o MWSDI n Multiple registries discovery n Ontologies used o o o OWL-S based approach n o Organized registries Semantic classification Logic inference is used for matching services … Web Service Discovery, Verma et al 2003: MWSDI Downloadable Tool: Lumina - Semantic Web Service Discovery 11

Semantic Web Process o o Web Services are application’s functionalities available on the Internet. n Examples: Zip Code, Booking Flights, etc. Single services has a limited utility n For traveling, it is not sufficient to book a Flight o o We must take care about booking the hotel, getting entertained, rental car, etc Web Services Composition n Collection of services in order to achieve a particular goal 12

Problem … o To achieve a given objective – sell my car, I may need more than one Web Service: n n n o Car Valuation service – WS 1 Car Auction Service – WS 2 Online Financial service – WS 3 All three WS need to interact seamlessly To achieve my goal Satya Sanket Sahoo 13

Semantic Web Process o Web Process n n Combine individual services to achieve a more complex goal Advantage o enables modular design o Implements the control and data flow between services n n n For example, Service A, B and C. B is dependent on A’s output message. A and C can be invoked at the same time OWL-S, WSMO, SWSF, WSDL-S, SAWSDL 14

Web Services Composition o o Necessity to achieve a predetermined goal that cannot be realized by a standalone service Problem’s Description n Travel Service o n n Composed of 3 atomic services: Airplane service, Hotel service and Car rental service The execution order of these 3 tasks is determined by a planner Proposed Environment involves these phases: o o Planning Discovery Optimization (Concerns this work) Execution 15

Web Services Composition o o WS discovery WS selection n Also non-functional criteria Qo. S n Multi-objective optimization approach n o WS composition Andrews T. et al. Specification: BPEL 4 WS - Business Process Execution Language for Web Services - Version 1. 1. OWL-S Coalition. OWL-S: Semantic Markup for Web Services. 16

Web Services Composition o Models to Compose Web Services n n BPEL 4 WS – Business Process Execution Language for Web Services Abstract and executable processes Andrews T. et al. Specification: BPEL 4 WS - Business Process Execution Language for Web Services - Version 1. 1. OWL-S Coalition. OWL-S: Semantic Markup for Web Services. 17

Web Services Composition o Two categories of Web Services Composition: n Workflow composition o Static workflow composition: n o EFlow (Casati, Ilnicki, et al. 2000) Dynamic workflow composition: n PPM (Polymorphic Process Model) (Schuster, Georgakopoulos, et al. 2000) 18

Automatic approaches to WS composition o AI Planning n n o o Golog – Logic Programming Language Planning Domain Definition Language (PDDL) – action value Rule-based plan generation – SWORD (Ponnekanti and Fox, 2002) Hierarchical Task Network (HTN) – SHOP 2 (Wu, Sirin, et al. 2003) Approach considering the user preferences Software agents 19

Approaches to WS composition o What about WS composition supported by Collaboration? 20