Practical Semantic Web and Linked Data Applications by Mark Watson - HTML preview

Preface

xi

1.

Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xi

2.

Portable Common Lisp Code Book Examples . . . . . . . . . . . . . xii

3.

Using the Common Lisp ASDF Package Manager . . . . . . . . . . . xii

4.

Information on the Companion Edition to this Book that Covers Java

and JVM Languages

. . . . . . . . . . . . . . . . . . . . . . . . . . xiii

5.

AllegroGraph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii

6.

Software License for Example Code in this Book . . . . . . . . . . . xiv

1. Introduction

1

1.1. Who is this Book Written For? . . . . . . . . . . . . . . . . . . . . .

1

1.2. Why a PDF Copy of this Book is Available Free on the Web . . . . .

3

1.3. Book Software

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3

1.4. Why Graph Data Representations are Better than the Relational Database

Model for Dealing with Rapidly Changing Data Requirements . . . .

4

1.5. What if You Use Other Programming Languages Other Than Lisp? . .

4

2. AllegroGraph Embedded Lisp Quick Start

7

2.1. Starting AllegroGraph

. . . . . . . . . . . . . . . . . . . . . . . . .

7

2.2. Working with RDF Data Stores . . . . . . . . . . . . . . . . . . . . .

8

2.2.1.

Creating Repositories . . . . . . . . . . . . . . . . . . . . . .

9

2.2.2.

AllegroGraph Lisp Reader Support for RDF . . . . . . . . . . 10

2.2.3.

Adding Triples . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.2.4.

Fetching Triples by ID . . . . . . . . . . . . . . . . . . . . . 11

2.2.5.

Printing Triples . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.2.6.

Using Cursors to Iterate Through Query Results . . . . . . . . 13

2.2.7.

Saving Triple Stores to Disk as XML, N-Triples, and N3 . . . 14

2.3. AllegroGraph’s Extensions to RDF . . . . . . . . . . . . . . . . . . . 14

2.3.1.

Examples Using Triple and Graph IDs . . . . . . . . . . . . . 15

2.3.2.

Support for Geo Location

. . . . . . . . . . . . . . . . . . . 16

2.3.3.

Support for Free Text Indexing . . . . . . . . . . . . . . . . . 19

2.3.4.

Comparing AllegroGraph With Other Semantic Web Frame-

works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2.4. AllegroGraph Quickstart Wrap Up . . . . . . . . . . . . . . . . . . . 21

iii

Contents

I.

Semantic Web Technologies

23

3. RDF

25

3.1. RDF Examples in N-Triple and N3 Formats . . . . . . . . . . . . . . 27

3.2. The RDF Namespace . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.2.1.

rdf:type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.2.2.

rdf:Property . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.3. Dereferenceable URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.4. RDF Wrap Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4. RDFS

33

4.1. Extending RDF with RDF Schema . . . . . . . . . . . . . . . . . . . 33

4.2. Modeling with RDFS . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.3. AllegroGraph RDFS++ Extensions . . . . . . . . . . . . . . . . . . . 36

4.3.1.

owl:sameAs . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.3.2.

owl:inverseOf . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.3.3.

owl:TransitiveProperty . . . . . . . . . . . . . . . . . . . . . 38

4.4. RDFS Wrapup

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5. The SPARQL Query Language

41

5.1. Example RDF Data in N3 Format

. . . . . . . . . . . . . . . . . . . 41

5.2. Example SPARQL SELECT Queries . . . . . . . . . . . . . . . . . . 44

5.3. Example SPARQL CONSTRUCT Queries . . . . . . . . . . . . . . . 46

5.4. Example SPARQL ASK Queries . . . . . . . . . . . . . . . . . . . . 46

5.5. Example SPARQL DESCRIBE Queries . . . . . . . . . . . . . . . . 46

5.6. Wrapup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

6. RDFS++ and OWL

49

6.1. Properties Supported In RDFS++ . . . . . . . . . . . . . . . . . . . . 49

6.1.1.

owl:sameAs . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

6.1.2.

owl:inverseOf . . . . . . . . . . . . . . . . . . . . . . . . . . 50

6.1.3.

owl:TransitiveProperty . . . . . . . . . . . . . . . . . . . . . 51

6.2. RDF, RDFS, and RDFS++ Modeling Wrap Up

. . . . . . . . . . . . 51

II. AllegroGraph Extended Tutorial

53

7. SPARQL Queries Using AllegroGraph APIs

55

7.1. Using Namespaces . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

7.2. Reading RDF Data From Files . . . . . . . . . . . . . . . . . . . . . 56

7.3. Lisp APIs for Queires . . . . . . . . . . . . . . . . . . . . . . . . . . 56

7.4. Wrap Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

8. AllegroGraph Reasoning System

59

8.1. Enabling RDFS++ Reasoning on a Triple Store . . . . . . . . . . . . 59

iv

Contents

8.2. Inferring New Triples: rdf:type vs. rdfs:subClassOf Example . . . . . 60

8.3. Using Inverse Properties . . . . . . . . . . . . . . . . . . . . . . . . 61

8.4. Using the Same As Property . . . . . . . . . . . . . . . . . . . . . . 63

8.5. Using the Transitive Property . . . . . . . . . . . . . . . . . . . . . . 63

8.6. Wrap Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

9. AllegroGraph Prolog Interface

67

III. Portable Common Lisp Utilities for Information Pro-

cessing

71

10. Linked Data and the World Wide Web

73

10.1. Linked Data Resources on the Web . . . . . . . . . . . . . . . . . . . 74

10.2. Publishing Linked Data . . . . . . . . . . . . . . . . . . . . . . . . . 74

10.3. Will Linked Data Become the Semantic Web? . . . . . . . . . . . . . 75

10.4. Linked Data Wrapup . . . . . . . . . . . . . . . . . . . . . . . . . . 75

11. Common Lisp Client Library for Open Calais

77

11.1. Open Calais Web Services Client . . . . . . . . . . . . . . . . . . . . 77

11.2. Storing Entity Data in an RDF Data Store . . . . . . . . . . . . . . . 80

11.3. Testing the Open Calais Demo System . . . . . . . . . . . . . . . . . 81

11.4. Open Calais Wrap Up . . . . . . . . . . . . . . . . . . . . . . . . . . 82

12. Common Lisp Client Library for Natural Language Processing

85

12.1. KnowledgeBooks.com Natural Language Processing Library . . . . . 85

12.2. KnowledgeBooks Natural Language Processing Library Wrapup . . . 87

13. Common Lisp Client Library for Freebase

89

13.1. Overview of Freebase . . . . . . . . . . . . . . . . . . . . . . . . . . 89

13.2. Accessing Freebase from Common Lisp . . . . . . . . . . . . . . . . 91

13.3. Freebase Wrapup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

14. Common Lisp Client Library for DBpedia

95

14.1. Interactively Querying DBpedia Using the Snorql Web Interface . . . 95

14.2. Interactively Finding Useful DBpedia Resources Using the gFacet

Browser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

14.3. The lookup.dbpedia.org Web Service . . . . . . . . . . . . . . . . . . 97

14.4. Using the AllegroGraph SPARQL Client Library to access DBpedia . 99

14.5. DBpedia Wrapup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

15. Library for GeoNames

101

15.1. Using the cl-geonames Library . . . . . . . . . . . . . . . . . . . . . 101

15.2. Geonames Wrapup . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

v

Contents

IV. Example Semantic Web Application

105

16. Semantic Web Portal Back End Services

107

16.1. Implementing the Back End APIs

. . . . . . . . . . . . . . . . . . . 108

16.2. Unit Testing the Backend Code . . . . . . . . . . . . . . . . . . . . . 110

16.3. Backend Wrapup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

17. Semantic Web Portal User Interface

113

17.1. Portable AllegroServe . . . . . . . . . . . . . . . . . . . . . . . . . . 113

17.2. Layout of CLP files for Web Application . . . . . . . . . . . . . . . . 113

17.3. Common Lisp Code for Web Application . . . . . . . . . . . . . . . 114

17.4. Web Application Wrap Up . . . . . . . . . . . . . . . . . . . . . . . 118

vi

List of Figures

1.1. Example Semantic Web Application . . . . . . . . . . . . . . . . . .

2

14.1. DBpedia Snorql Web Interface . . . . . . . . . . . . . . . . . . . . . 96

14.2. DBpedia Graph Facet Viewer . . . . . . . . . . . . . . . . . . . . . . 98

14.3. DBpedia Graph Facet Viewer after selecting a resource . . . . . . . . 98

17.1. Example Semantic Web Application Login Page . . . . . . . . . . . . 114

17.2. Example File Upload Page . . . . . . . . . . . . . . . . . . . . . . . 116

17.3. Example Application Search Page . . . . . . . . . . . . . . . . . . . 118

vii

List of Tables

13.1. Subset of Freebase API Arguments . . . . . . . . . . . . . . . . . . . 90

ix