Enabling Semantic Web Services

Enabling Semantic Web Services

DieterFensel HolgerLausen AxelPolleres Jos de Bruijn Michael Stollberg Dumitru Roman John Domingue Enabling Semantic Web Services The Web Service Modeling Ontology With 41 Figures and 2 Tables 123

Dieter Fensel Holger Lausen Jos de Bruijn Michael Stollberg Dumitru Roman Technikerstr. 21a 6020 Innsbruck, Austria dieter.fensel@deri.org holger.lausen@deri.org jos.debruijn@deri.org michael.stollberg@deri.org dumitru.roman@deri.org Axel Polleres Área de Ciencia de la Computación e Inteligencia Artificial Universidad Rey Juan Carlos 28933 Móstoles (Madrid), España axel@polleres.net John Domingue Knowledge Media Institute The Open University Walton Hall Milton Keynes, MK7 6AA, United Kingdom j.b.domingue@open.ac.uk Library of Congress Control Number: 2006932416 ACM Computing Classification (1998): H.4, H.3, D.2, I.2 ISBN-10 3-540-34519-1 Springer Berlin Heidelberg New York ISBN-13 978-3-540-34519-0 Springer Berlin Heidelberg New York This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable for prosecution under the German Copyright Law. Springer is a part of Springer Science+Business Media springer.com Springer-Verlag Berlin Heidelberg 2007 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Typesetting: by the Authors Production: LE-TEX Jelonek, Schmidt & Vöckler GbR, Leipzig Cover: KünkelLopka, Heidelberg Printed on acid-free paper 45/3100YL - 5 4 3 2 1 0

Preface Motivation The constant driving factor behind the development of the Internet from its very beginning has been the combination of distributed data and software applications. The distribution of data has reached unforeseen dimensions with the development of the World Wide Web. On the basis of agreed standards, people are able to share and distribute information in a globally accessible, scalable fashion. The distribution of applications however, has more complex needs. You need agreed protocols and interfaces between distributed software components and, last but not least the data exchanged by these components must be machine-readable and understandable. To this end, service-oriented computing has become one of the predominant factors in current IT research and development efforts over the last few years. Standardization in this area has already made its way out of the research labs into industrial strength technologies and tools. Again, Web technologies prove to be a good starting point: Web services seem to be the middleware solution of the future for enabling the development of highly interoperable, distributed software solutions: the new technologies subsumed under this common term promise easy application integration by means of languages such as XML, and a common communication platform by relying on widely used Web protocols. While developments around Web services and service-oriented architectures provide the underlying infrastructure, another field which promises nothing less than the next generation of the Web is gaining momentum: researchers worldwide are currently working on the Semantic Web, a Web for machines, where not only is data distributed for human consumption, but also the data on the Web will be machine-processable. Naturally, these two lines of research fit together; still it seems unclear how to combine Web services and the Semantic Web in the most fruitful way.

VI Preface However, several promising results from numerous recent EU projects and efforts within the World Wide Web Consortium show the direction. Goals The goal of this book is to provide an insight into and an understanding of the problems faced by Web services and service-oriented architectures, as well as the promises and solutions of the Semantic Web. We focus particularly on the Web Service Modeling Ontology (WSMO), which provides a comprehensive conceptual framework for the fruitful combination of Semantic Web technologies and Web services. With the present book we want to give an overall understanding of the WSMO framework and show how it can be applied to the problems of serviceoriented architectures. It is not a ready-to-install user manual for Semantic Web services that is provided with this book, but rather an in-depth introduction. While many of the related technologies and standards are still under development we nevertheless think it is not too early for such a book: it is important to create an awareness of this technology and think about it today rather than tomorrow. The technology might not be at an industrial strength maturity yet, but the problems are already. Intended Audience This book is aimed at providing beneficial insights to persons with various levels of knowledge. On the one hand, by giving an exhaustive overview of the history and development of the underlying technologies, we aim to guide nonexperts in realizing the potential benefits of Semantic Web services, and to give them a good overview of the field. On the other hand, we provide plenty of detail about the Web Service Modeling Ontology, the state of its realization, its underlying language, and ongoing tool support and implementation efforts. By a thorough analysis of and comparison with all major related approaches, we aim also to give the reader a glance at different ideas, and at the possibility of future convergence of these technologies. Organisation of this Book We have divided the book in three main parts: Part I provides an introduction to the field and its history. We cover basic Web technologies, Web services and their predecessors, and the state of research and standardization in the Semantic Web field. Readers familiar with these basics or parts of them, can choose to skip all or parts of this Part.

Preface VII Part II is dedicated to the realization of Semantic Web services. At the core of this part of the book is a description of the Web Service Modeling Ontology and its language. We shall discuss in detail how WSMO and related technologies aim to address conceptually the problems of service-oriented architectures by exploiting semantic annotations. Part III is devoted to tools and applications and illustrates the practical developments around WSMO and Semantic Web service technologies in general. As opposed to the more abstract views in Part II, we aim to provide pointers to ready-to-use tools and to interesting prototypes in this part, and hope to encourage many interested readers to exploit and possibly deploy the technologies presented in practice. Acknowledgments The work presented in this book has been funded by the European Commission under the SWWS Project (IST-2001-37134), in addition to contributions from several other EU projects, namely, Knowledge Web (FP6-507482), DIP (FP6-507483), and SEKT (IP-2003-506826). The majority of the research that is described in this publication must be accredited to the tireless efforts of the WSMO, WSML, WSMX, and WSMT working groups, to whom we remain gratefully indebted for their valuable discussion and helpful advice. We must also express the same gratitude to several members of the OASIS consortium, particularly the SEE technical committee. Though we are unable to mention so very many whose contributions deserve acknowledgment, this section would be incomplete as would the respective sections of this book without recognizing the contributions of our colleagues, Uwe Keller, Mick Kerrigan, Jacek Kopecký, and Barry Norton. Special thanks also goes to Graham Hench for his enduring proofreading and patient editorial efforts. Finally, to all those not mentioned and to any we may have forgotten we offer our sincerest thank you. The authors, April 2006

Contents Part I Foundations 1 Introduction... 3 2 The World Wide Web... 7 2.1 History... 7 2.2 TheBuildingBlocks:URIs,HTTP,andHTML... 10 2.3 FromHTMLtoXML... 14 2.4 Summary... 24 3 The Semantic Web... 25 3.1 OntologiesandtheSemanticWeb... 27 3.2 TheResourceDescriptionFramework... 31 3.3 TheWebOntologyLanguageOWL... 33 3.4 RulesfortheSemanticWeb... 34 3.5 Summary... 36 4 Web Services... 37 4.1 TerminologyandPrinciples... 39 4.2 TheOriginsofWebServices... 40 4.3 TheWebServiceTechnologyStack... 42 4.4 WebServicesinReality... 49 4.5 What smissinginwebservices?... 50 4.6 Summary... 53 Part II The Web Service Modeling Ontology 5 Introduction to WSMO... 57 5.1 WSMODesignPrinciples... 57 5.2 Top-LevelElementsofWSMO... 59

X Contents 5.3 TheLanguageforDefiningWSMO... 60 6 The Concepts of WSMO... 63 6.1 Ontologies... 63 6.2 WebServices... 67 6.3 Goals... 74 6.4 Mediators... 75 6.5 NonfunctionalProperties... 78 6.6 Summary... 81 7 WSML a Language for WSMO... 83 7.1 TheWSMLLayering... 84 7.2 GeneralWSMLSyntax... 85 7.3 WSMLSemantics... 93 7.4 WSMLExchangeSyntaxes... 94 7.5 KeyFeaturesofWSML... 97 7.6 RelationtoRDF(S)andOWL... 98 7.7 Summary... 99 8 Related Work in the Area of Semantic Web Service Frameworks...101 8.1 OWL-S...101 8.2 SWSF...104 8.3 WSDL-S...107 8.4 Summary...109 Part III Tools and Applications 9 Semantic Web Service Usage Tasks in WSMO...113 9.1 TheVirtualTravelAgencyScenario...113 9.2 Discovery...115 9.3 Mediation...124 9.4 Composition...132 9.5 Grounding and Execution................................ 135 10 Tools...141 10.1 Infrastructure...141 10.2 DesignTools...145 10.3 ExecutionEnvironments...151 10.4 Summary...156

Contents XI 11 Applications of WSMO...157 11.1 E-Commerce...157 11.2 E-Government...165 11.3 E-Banking...166 11.4 Summary...168 12 Conclusion and Outlook...169 12.1 SemanticWebServicesUsingWSMO...169 12.2 StandardizationEfforts...170 12.3 Industrial Collaboration.................................. 173 12.4 AlternativestoClassicalWebServices...174 References...177 Index...187

List of Figures 2.1 Gopher thefirst netbrowser... 8 2.2 Mosaic thefirstgraphicalwebbrowser... 10 2.3 HTML document and corresponding layout in a Web browser.. 13 2.4 An HTML table: tags do not reflect the meaning of the content 15 2.5 AnXMLtree... 17 2.6 XSLT:convertingbetweendifferentXMLformats... 23 3.1 TheSemanticWeblanguagelayercake... 26 3.2 Exampleis-ahierarchy(ortaxonomy)... 28 3.3 ExampleRDFgraph... 31 3.4 ExampleRDF/XMLserialization... 32 3.5 RDFS ontology of persons and working group members....... 32 4.1 Webservicearchitecture... 38 4.2 StructuresofWSDL1.1andWSDL2.0... 45 4.3 The GlobalWeather service viewed in an UDDI browser....... 48 4.4 TheevolutionoftheWeb... 50 5.1 WSMOcoreelements... 59 5.2 TherelationbetweenWSMOandMOF... 60 6.1 WSMOWebservice generaldescription... 67 7.1 WSMLvariantsandlayering... 84 8.1 OWL-Sconceptualmodel...102 8.2 ThelayeredstructureofSWSL-Rules[9]...106 8.3 Schematic illustration of how WSDL-S provides links to domainmodels...107 9.1 OverviewoftheuseoftheVTA...114 9.2 Thethreemajorprocessesofheuristicclassification...118

XIV List of Figures 9.3 Thethreemajorprocessesinservicediscovery...119 9.4 Matchmaking notions for semantically enabled discovery...... 124 9.5 Dimensionsofmediation...125 9.6 Processmediationpatterns...128 9.7 Exampleofprocess-levelmediation...129 9.8 WSMOmediatortopology...131 9.9 Approaches to data grounding............................. 137 10.1 ArchitectureoftheWSML2Reasonerframework...144 10.2 TheWSMLonlinereasoningservice...145 10.3 The Eclipse platform and the WSMO tools developed on it.... 146 10.4 TheWebServiceModelingToolkit...148 10.5 Creating mappings in the data mediation plug-in............. 148 10.6 ConcepteditorinWSMOStudio...149 10.7 DERI Ontology Management Environment (DOME).......... 150 10.8 WSMXcomponents...152 11.1 OverviewofaVISP...163 11.2 SemanticWebservicesine-government...166