Glen Hart • Catherine Dolbear Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2013 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed in the United States of America on acid-free paper Version Date: 2012904 International Standard Book Number: 978-1-4398-6995-6 (Hardback) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. The Open Access version of this book, available at www.taylorfrancis.com, has been made available under a Creative Commons Attribution-Non Commercial-No Derivatives 4.0 license. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging‑in‑Publication Data Hart, Glen, 1959- Linked data : A Geographic Perspective / Glen Hart and Catherine Dolbear. p. cm. Includes bibliographical references and index. ISBN 978-1-4398-6995-6 1. Geography--Data processing. 2. Geography--Computer network resources. 3. Semantic Web. I. Dolbear, Catherine, 1976- II. Title. G70.2.H37 2013 910.285’4678--dc23 2012027810 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com What is written without effort is in general read without pleasure. Samuel Johnson We hope we have made enough effort to bring some pleasure in reading. Glen Hart and Catherine Dolbear Contents Preface......................................................................................................................xv About the Authors ...................................................................................................xix Chapter 1 A Gentle Beginning..............................................................................1 1.1 What This Book Is About and Who It Is For ............................1 1.2 Geography and the Semantic Web ............................................2 1.2.1 Geographic Information ...............................................2 1.2.2 The Semantic Web .......................................................3 1.3 GI in the Semantic Web .............................................................3 1.4 Examples ...................................................................................4 1.5 Conventions Used in the Book ..................................................5 1.6 Structure of the Book ................................................................7 1.7 A Last Thought about How to Read This Book ........................7 Chapter 2 Linked Data and the Semantic Web .....................................................9 2.1 Introduction ...............................................................................9 2.2 From a Web of Documents to a Web of Knowledge .................9 2.3 Early History and the Development of the Semantic Web ......12 2.4 Semantic Web Benefits ............................................................ 16 2.4.1 Data Integration .......................................................... 16 2.4.2 Data Repurposing ....................................................... 17 2.4.3 Data Collection, Classification, and Quality Control ... 17 2.4.4 Data Publishing and Discovery .................................. 18 2.5 How It Works ........................................................................... 19 2.6 Recent Trends in the Field ....................................................... 21 2.7 Summing Up and Signposts to the Next Chapter ....................23 Notes ...................................................................................................23 Chapter 3 Geographic Information .....................................................................25 3.1 Introduction .............................................................................25 3.2 What Is Geographic Information? ...........................................25 3.3 The Many Forms of GI ............................................................26 3.3.1 Geometry ....................................................................26 3.3.1.1 Raster ..........................................................26 3.3.1.2 Vector ..........................................................27 3.3.2 Topology and Mereology............................................28 3.3.3 Textual Representations .............................................29 3.3.3.1 Description ..................................................29 3.3.3.2 Classification ...............................................30 vii viii Contents 3.3.3.3 Direction ..................................................... 31 3.3.3.4 Address ....................................................... 31 3.4 Representations and Uses of GI ............................................... 33 3.4.1 Maps ........................................................................... 33 3.4.2 Gazetteers ................................................................... 35 3.4.3 Terrain Models and Three Dimensions ......................36 3.4.4 Digital Feature Models ...............................................36 3.5 A Brief History of Geographic Information ............................37 3.5.1 A Traditional Story: GI and GIS ................................37 3.5.1.1 Geographic Information Systems ...............37 3.5.1.2 Standards Develop ......................................40 3.5.1.3 The Web ......................................................40 3.5.1.4 Spatial Data Infrastructures ........................ 41 3.5.2 GI: A History of the Web and Spatial Coincidence ....42 3.5.2.1 Open Government Data ..............................46 3.5.3 The Formal and Informal Together ............................ 47 3.6 Summary .................................................................................49 Notes ...................................................................................................50 Chapter 4 Geographic Information in an Open World ....................................... 51 4.1 Introduction ............................................................................. 51 4.2 Principles ................................................................................. 51 4.2.1 Semantic Web ............................................................. 51 4.2.2 Geographic Information ............................................. 52 4.3 Applying the Semantic Web to GI ...........................................56 4.3.1 Example ......................................................................56 4.3.1.1 Obtain Appropriate Datasets ......................56 4.3.1.2 Load the Data .............................................57 4.3.1.3 Conduct the Spatial Analysis ......................57 4.3.1.4 Observations and Discussion ......................58 4.3.2 Topological Relationships ..........................................59 4.4 Important Observations ........................................................... 61 4.5 Summary .................................................................................63 Notes ...................................................................................................64 Chapter 5 The Resource Description Framework ...............................................65 5.1 Introduction .............................................................................65 5.2 RDF: The Purpose ...................................................................65 5.3 A Word about Identity .............................................................66 5.4 The RDF Data Model ..............................................................67 5.5 RDF Serialization .................................................................... 71 5.5.1 RDF/XML .................................................................. 71 5.5.2 Turtle .......................................................................... 75 Contents ix 5.5.3 N-Triples ..................................................................... 76 5.5.4 RDFa .......................................................................... 76 5.6 RDFS .......................................................................................78 5.6.1 Concepts and Instances: Instantiation and Hierarchy in RDFS .....................................................78 5.6.2 Vocabularies and Ontology ........................................78 5.6.3 RDFS Syntax: Classes and Properties .......................79 5.6.4 Subproperties, Domain, and Range ...........................80 5.6.5 RDF Containers and Collections................................80 5.6.6 RDFS Utility Properties ............................................. 81 5.7 Popular RDFS Vocabularies ....................................................82 5.7.1 Geo RDF ....................................................................83