General Introduction for Semantic Web and Linked Open Data

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2012 INTERNATIONAL ASIAN SUMMER SCHOOL IN LINKED DATA  …

2012 INTERNATIONAL ASIAN SUMMER SCHOOL IN LINKED DATA 
IASLOD 2012, August 13-17, 2012, KAIST, Daejeon, Korea

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  • 1. 2012 INTERNATIONAL ASIAN SUMMER SCHOOL IN LINKED DATA IASLOD 2012, August 13-17, 2012, KAIST, Daejeon, Korea General Introductionfor Semantic Web and Linked Open Data Hideaki Takeda National Institute of Informatics takeda@nii.ac.jp Hideaki Takeda / National Institute of Informatics
  • 2. Semantic Web and Linked Data• Semantic Web – What is Semantic Web – How to realize Semantic Web • Metadata • RDF • RDFS • OWL• Linked Data – What is Linked Data? – The State-of-the-Art of Linked Data • Linking Open Data (LOD) – How to use Linked Data • Linked Data Browser • Linked Data Search Engine • Linked Data Applications – How to use RDF • RDFa – SPARQL Hideaki Takeda / National Institute of Informatics
  • 3. Semantic Web Hideaki Takeda / National Institute of Informatics
  • 4. The Aim of The Semantic Web• "The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation." The Semantic Web, Scientific American, May 2001, Tim Berners-Lee, James Hendler and Ora Lassila• The Semantic Web is a vision: the idea of having data on the web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration and reuse of data across various applications. http://www.w3.org/2001/sw/ Hideaki Takeda / National Institute of Informatics
  • 5. Semantic Web• Realization of various information exchanging via Web Automation 自動化 Integration 統合 Re-use of data データの再利用 Hideaki Takeda / National Institute of Informatics
  • 6. Next Generation Web?• Evolution of Web – HTML: Web for Display – XML: Web with Syntax – ?? : Web with Semantics• Why should we embed semantics into Web? From – Web for Human To – Web for human and machines cf. Web for machines Hideaki Takeda / National Institute of Informatics
  • 7. A brief introduction of XML• Limitation of HTML – Chaos by mixture of displaying and text structures • e.g., – <h3></h3> should be used for “the third-level heading”, but are often used just for bigger fonts – <b></b> is specifying “bold” , not “emphasis”. – Fixed Structure • e.g., – If you need <h7></h7>…. – I need a structure just for my data <h1> A list of lectures</h1> <h2> Knowledge Sharing Systems</h2> <h3> Lecturer: Hideaki Takeda</h3> <h3>Wednesday 3rd</h3> Hideaki Takeda / National Institute of Informatics
  • 8. XML• XML(eXtensible Markup Language) – Can define original tags – Represent logical structures of data • DTD – Do not include style information <lecturelist> • XST <lecture> <title id=1234> Knowledge Sharing Systems</title> <lecturer> Hideaki Takeda</lecturer> <schedule> <week>Wednesday</week> <time>3rd</time> </lecture> ... </lecturelist> Hideaki Takeda / National Institute of Informatics
  • 9. Whey is XML not sufficient?<person> <個人> <name> Hideaki Takeda</name> <名前>Hideaki Takeda</名前> <age> 20</age> <年齢> 20</年齢></person> </個人>• What are specified by “person” and “name” ?• Is “name” and “名前” the same?• Is this description sufficient as a description for “person”?• …• In short, syntax alone cannot solve these problems Hideaki Takeda / National Institute of Informatics
  • 10. Architecture for the Semantic Web Tim Berners-Lee http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/ Hideaki Takeda / National Institute of Informatics
  • 11. How to describe “meaning”?• Need to describe “information on information” – “Meaning of something” is a description (“meaning”) to a description (“something”) in computers – Metadata • Data about data• Need to architecture for common understanding – Syntax (language or scheme) – Vocabulary (ontology) Hideaki Takeda / National Institute of Informatics
  • 12. Metadata• What is metadata? – Data about data – What one can say about any information object• What is described as metadata? – Content relates to what the object contains or is about, and is intrinsic to an information object. – Context indicates the who, what, why, where, how aspects associated with the objects creation and is extrinsic to an information object. – Structure relates to the formal set of associations within or among individual information objects and can be intrinsic or extrinsic Setting the State, Anne J.Gilliand-Swetland, Introduction to Metadata – Pathways to Digital Information, Murthsa Baca (ed.), Getty Information Institute. Hideaki Takeda / National Institute of Informatics
  • 13. Metadata• Metadata to individual information objects – Bibliography,Dublin Core• Metadata to part or structure of information objects – Drawings,RDF,RDFS, OWL Type:tractor Owner:Taro Product year:2002 Body Axis: Connect body to wheel Wheel Hideaki Takeda / National Institute of Informatics
  • 14. A Layer model for Semantic Web• RDF (Resource Description Framework) – The most primitive model for metadata description • SVO model • Entity-Relation Model • Semantic net• RDF Schema – Addition of “concept” to RDF • class-subclass,constraints• OWL – More general concept description language • Logical consistency • Various class expressions • Various constraints• DAML-S – Descriptions on processes Tim Berners-Lee http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/ Hideaki Takeda / National Institute of Informatics
  • 15. RDF (Resource Description Framework)• A framework to describe metadata• Separation of model and syntax• W3C Recommendation (2004) Hideaki Takeda / National Institute of Informatics
  • 16. RDF Model• Element – Resource: • URI(Universal Resource Identifier) • Literal(string) – No need to be specified by Web – Property: • Attribute when describing resources • URI or Literal just as Resource – Statement: triad of resource, property, and resource Hideaki Takeda / National Institute of Informatics
  • 17. RDF model• Statement – Creator of http://www-kasm.nii.ac.jp/~takeda is “Hideaki Takeda”• Structure – Resource (subject): http://www-kasm.nii.ac.jp/~takeda – Property (predicate): Creator – Value (object): “Hideaki Takeda” Creator http://www-kasm.nii.ac.jp/~takeda “Hideaki Takeda” Resource Property Value Hideaki Takeda / National Institute of Informatics
  • 18. RDF model• Creator of http://www-kasm.nii.ac.jp/~takeda is http://www.nii.ac.jp/staffid/123456 which has name “Hideaki Takeda” and email “takeda@nii.ac.jp” . Creator http://www-kasm.nii.ac.jp/~takeda http://www.nii.ac.jp/staffid/123456 name email “Hideaki Takeda” “takeda@nii.ac.jp” Hideaki Takeda / National Institute of Informatics
  • 19. RDF model• Creator of http://www-kasm.nii.ac.jp/~takeda has name “Hideaki Takeda” email “takeda@nii.ac.jp” . Creator http://www-kasm.nii.ac.jp/~takeda name email “Hideaki Takeda” “takeda@nii.ac.jp” Hideaki Takeda / National Institute of Informatics
  • 20. RDF syntax• Creator of http://www-kasm.nii.ac.jp/~takeda is “Hideaki Takeda” Creator http://www-kasm.nii.ac.jp/~takeda “Hideaki Takeda” Resource Property Value <?xml version="1.0"?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://dublincore.org/2001/08/14/dces#"> <rdf:Description about="http://www-kasm.nii.ac.jp/~takeda"> <dc:Creator>Hideaki Takeda</dc:Creator> </rdf:Description> </rdf:RDF> <rdf:RDF> <rdf:Description about="http://www-kasm.nii.ac.jp/~takeda"> <dc:Creator rdf:resource=“Hideaki Takeda” /> </rdf:Description> </rdf:RDF> Hideaki Takeda / National Institute of Informatics
  • 21. RDFS (RDF Schema)• Stronger knowledge representation model – RDF: ER model,semantic net – RDF Schema: Frame model,object-oriented paradigm • Minimal definition • Property-centered approach• RDFS is defined as extension of RDF• RDFS gives definitions of RDF descriptions Hideaki Takeda / National Institute of Informatics
  • 22. RDFS• Class Definition – rdfs:Resource – rdfs:Class – rdf:Property – rdfs:ConstraintProperty – rdfs:Literal• Property Definition – rdf:type – rdfs:subClassOf – rdfs:subPropertyOf – rdfs:comment – rdfs:label – rdfs:seeAlso – rdfs:isDefinedBy• ConstraintProperty Definition – rdfs:range RDFS Structure by RDF – rdfs:domain Resource Description Framework(RDF) Schema Specification 1.0 http://www.w3.org/TR/2000/CR-rdf-schema-20000327/ Hideaki Takeda / National Institute of Informatics
  • 23. RDF Schema• rdfs:Class  Range• rdfs:SubclassOf  Only one – Detailed class  No cardinality – Multiple  Domain – Transivity  Multiple (or)• rdf:type – Indicate an instance of a class• rdf:property – Attribute• rdfs:subPropertyOf – Detailed property – Transivity Hideaki Takeda / National Institute of Informatics
  • 24. <rdf:RDF xml:lang="en" RDF Schema xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" “The class of person” Animal s xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"> rdfs:comment<rdfs:Class rdf:ID="Person"> Person <rdfs:comment>The class of people.</rdfs:comment> d d <rdfs:subClassOf rdf:resource="http://www.w3.org/ maritalStatus d 2000/03/example/ r ssn classes#Animal"/> age</rdfs:Class> MaritalStatus r<rdf:Property ID="maritalStatus"> rdfs:comment <rdfs:range rdf:resource="#MaritalStatus"/> Integer <rdfs:domain rdf:resource="#Person"/> t t</rdf:Property> Married “Social Security Number”<rdf:Property ID="ssn"> t Single <rdfs:comment>Social Security Number</rdfs:comment> Windowed <rdfs:range t = rdf:type rdf:resource="http://www.w3.org/2000/03/example/classes#Integer"/> t d = rdfs:domain <rdfs:domain rdf:resource="#Person"/> Divorced r = rdfs:range</rdf:Property> = class<rdf:Property ID="age"> = class instance <rdfs:range = property rdf:resource="http://www.w3.org/2000/03/example/classes#Integer"/> <rdfs:domain rdf:resource="#Person"/></rdf:Property><rdfs:Class rdf:ID="MaritalStatus"/><MaritalStatus rdf:ID="Married"/><MaritalStatus rdf:ID="Divorced"/> Resource Description Framework(RDF) Schema Specification 1.0<MaritalStatus rdf:ID="Single"/> http://www.w3.org/TR/2000/CR-rdf-schema-20000327/<MaritalStatus rdf:ID="Widowed"/></rdf:RDF> Hideaki Takeda / National Institute of Informatics
  • 25. OWL(Web Ontology Language)• More general knowledge representation• Based on Description Logics• Features – Class • Necessary condition / necessary and sufficient condition • Class expression: – Constraint by property » Like slot definition of a class » Type constraint (all/some), cardinality, typed cardinality – Logical operation of classes: union, intersection, negation – Property • Multiple ranges and domains • Specifying meta-property – Import of definitions Hideaki Takeda / National Institute of Informatics
  • 26. Linked Data Hideaki Takeda / National Institute of Informatics
  • 27. Linked Data• What is Linked Data?• The State-of-the-Art of Linked Data – Linking Open Data (LOD)• How to use Linked Data – Linked Data Browser – Linked Data Search Engine – Linked Data Applications• How to use RDF – RDFa – SPARQL Hideaki Takeda / National Institute of Informatics
  • 28. Linked Data• What is Linked Data?• The State-of-the-Art of Linked Data – Linking Open Data (LOD)• How to use Linked Data – Linked Data Browser – Linked Data Search Engine – Linked Data Applications• How to use RDF – RDFa – SPARQL Hideaki Takeda / National Institute of Informatics
  • 29. Architecture for the Semantic Web The world of classes (Ontologies) The world of instances (Linked Data) Tim Berners-Lee http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/ Hideaki Takeda / National Institute of Informatics
  • 30. Layers of Semantic Web• Ontology – Descriptions on classes – RDFS, OWL – Challenges for ontology building • Ontology building is difficult by nature – Consistency, comprehensiveness, logicality • Alignment of ontologies is more difficult Descriptions on classes Ontology インスタンスに関する記述 Linked Data Tim Berners-Lee http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/ Hideaki Takeda / National Institute of Informatics
  • 31. Layers of Semantic Web• Linked Data – Descriptions on instances (individuals) – RDF + (RDFS, OWL) – Pros for Linked Data • Easy to write (mainly fact description) • Easy to link (fact to fact link) – Cons for Linked Data • Difficult to describe complex structures • Still need for class description (-> ontology) Descriptions on classes Ontology Description on instances Linked Data Tim Berners-Lee http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/ Hideaki Takeda / National Institute of Informatics
  • 32. Linked Data Linked Data is “Web of Data” – Data published as RDF – Can refer from outside• The four rules for Linked Data Hideaki Takeda / National Institute of Informatics
  • 33. Linked Data• The four rules for Linked Data – Use URIs as names for things • Give a URI to every object in the world! – Use HTTP URIs so that people can look up those names. • Don’t use URN – When someone looks up a URI, provide useful information, using the standards (RDF, SPARQL) • Provide machine-readable data for URI – Include links to other URIs. so that they can discover more things. • Make data linked together just like Web Linked Data, TBL, http://www.w3.org/DesignIssues/LinkedData.html Hideaki Takeda / National Institute of Informatics
  • 34. Linked Data• What is Linked Data?• The State-of-the-Art of Linked Data – Linking Open Data (LOD)• How to use Linked Data – Linked Data Browser – Linked Data Search Engine – Linked Data Applications• How to use RDF – RDFa – SPARQL Hideaki Takeda / National Institute of Informatics
  • 35. Linking Open Data (LOD)• The project to collect published Linked Data• Major Linked Data• (Translated from the original resources) – Dbpedia (Wikipedia) 270 Million Triples – Geonames:Geo names and their latitudes and longitudes, 93 Million Triples – MusicBrainz:Music – WordNet:Dictionary – DBLP bibliography:Bibliography for technical papers. 28 Million Triples – US Census Data: 1 Billion Triples• (Crawling) – FOAF (Friend Of A Friend)• (Wrapper) – Flickr Wrapper Hideaki Takeda / National Institute of Informatics
  • 36. Hideaki Takeda / National Institute of Informatics
  • 37. Hideaki Takeda / National Institute of Informatics
  • 38. LOD Cloud(Linking Open Data) Hideaki Takeda / National Institute of Informatics
  • 39. http://dbpedia.org/page/TokyoHideaki Takeda / National Institute of Informatics
  • 40. http://en.wikipedia.org/wiki/TokyoHideaki Takeda / National Institute of Informatics
  • 41. Hideaki Takeda / National Institute of Informatics
  • 42. Hideaki Takeda / National Institute of Informatics
  • 43. Linked Data• What is Linked Data?• The State-of-the-Art of Linked Data – Linking Open Data (LOD)• How to use Linked Data – Linked Data Browser – Linked Data Search Engine – Linked Data Applications• How to use RDF – RDFa – SPARQL Hideaki Takeda / National Institute of Informatics
  • 44. How to use Linked DataLinked Data Linked Data Linked Data Browser Mashup Search EngineThings Things Things Things Things Hideaki Takeda / National Institute of Informatics
  • 45. Linked Data• What is Linked Data?• The State-of-the-Art of Linked Data – Linking Open Data (LOD)• How to use Linked Data – Linked Data Browser – Linked Data Search Engine – Linked Data Applications• How to use RDF – RDFa – SPARQL Hideaki Takeda / National Institute of Informatics
  • 46. Linked Data Browser• Browse linked data just as browsing web pages – Show RDF data – Prompt links to follow• System/Service – Mables • Display data by following links – Tabulator • Firefox plugin/online • Adding information in a single page – Sig.ma • Showing RDF resources which can be operated Hideaki Takeda / National Institute of Informatics
  • 47. Hideaki Takeda / National Institute of Informatics
  • 48. Tabulator Hideaki Takeda / National Institute of Informatics
  • 49. Hideaki Takeda / National Institute of Informatics
  • 50. Linked Data• What is Linked Data?• The State-of-the-Art of Linked Data – Linking Open Data (LOD)• How to use Linked Data – Linked Data Browser – Linked Data Search Engine – Linked Data Applications• How to use RDF – RDFa – SPARQL Hideaki Takeda / National Institute of Informatics
  • 51. Linked Data Search Engine• Search RDF data with crawled data set – Swoogle – Sindice – watson Hideaki Takeda / National Institute of Informatics
  • 52. http://sindice.com/Hideaki Takeda / National Institute of Informatics
  • 53. Hideaki Takeda / National Institute of Informatics
  • 54. Linked Data• What is Linked Data?• The State-of-the-Art of Linked Data – Linking Open Data (LOD)• How to use Linked Data – Linked Data Browser – Linked Data Search Engine – Linked Data Applications• How to use RDF – RDFa – SPARQL Hideaki Takeda / National Institute of Informatics
  • 55. How to use Linked Data• Semantic Data Mash-up Applications – SemaPlorer • http://btc.isweb.uni-koblenz.de/ – Dbpedia Mobile • http://wiki.dbpedia.org/DBpediaMobile – Bio2RDF • http://bio2rdf.org/ Hideaki Takeda / National Institute of Informatics
  • 56. DBpedia Mobile Hideaki Takeda / National Institute of Informatics
  • 57. Bio2RDF• Search LOD in bioscience• Translate data into RDF if not Hideaki Takeda / National Institute of Informatics
  • 58. Bio2RDF Hideaki Takeda / National Institute of Informatics
  • 59. Linked Data• What is Linked Data?• The State-of-the-Art of Linked Data – Linking Open Data (LOD)• How to use Linked Data – Linked Data Browser – Linked Data Search Engine – Linked Data Applications• How to use RDF – RDFa – SPARQL Hideaki Takeda / National Institute of Informatics
  • 60. RDFa• Add extra structured content to the (X)HTML pages – adds new (X)HTML/XML attributes • “RDF in attributes” – Programs can extract those and turn into RDF – Flexibility for using Literals and URI resources Hideaki Takeda / National Institute of Informatics
  • 61. Principles of RDFa• RDF contents are defined through XML attributes (no elements)• XML/HTML tree structure is used• Various attributes are defined by RDFa – Some attributes (@href, @rel) are also reused• The text content can be also reused Hideaki Takeda / National Institute of Informatics
  • 62. Examples http://example.com/alice/posts/trouble_with_bob <div xmlns:dc="http://purl.org/dc/elements/1.1/"> <h2 property="dc:title">The trouble with Bob</h2> <h3 property="dc:creator">Alice</h3> ... </div>In N3<http://www.example.com/alice/posts/trouble_with_bob> <http://purl.org/dc/elements/1.1/title> "The Trouble with Bob"; <http://purl.org/dc/elements/1.1/creator> "Alice" . Hideaki Takeda / National Institute of Informatics
  • 63. <div xmlns:dc="http://purl.org/dc/elements/1.1/"> <div about="/alice/posts/trouble_with_bob"> <h2 property="dc:title">The trouble with Bob</h2> <h3 property="dc:creator">Alice</h3> ... </div> <div about="/alice/posts/jos_barbecue"> <h2 property="dc:title">Jos Barbecue</h2> <h3 property="dc:creator">Eve</h3> ... </div> ...</div> Hideaki Takeda / National Institute of Informatics
  • 64. <div about="/alice/posts/trouble_with_bob"> <h2 property="dc:title">The trouble with Bob</h2> The trouble with Bob is that he takes much better photos than I do: <div about="http://example.com/bob/photos/sunset.jpg"> <img src="http://example.com/bob/photos/sunset.jpg" /> <span property="dc:title">Beautiful Sunset</span> by <span property="dc:creator">Bob</span>. </div></div> Hideaki Takeda / National Institute of Informatics
  • 65. <div typeof="foaf:Person" xmlns:foaf="http://xmlns.com/foaf/0.1/"> <p property="foaf:name"> Alice Birpemswick </p> <p> Email: <a rel="foaf:mbox" href="mailto:alice@example.com">alice@example.com</a></p> <p> Phone: <a rel="foaf:phone" href="tel:+1-617-555-7332">+1 617.555.7332</a> </p></div> Hideaki Takeda / National Institute of Informatics
  • 66. <div xmlns:foaf="http://xmlns.com/foaf/0.1/" about="#me" rel="foaf:knows"> <ul> <li typeof="foaf:Person"> <a property="foaf:name" rel="foaf:homepage" href="http://example.com/bob">Bob</a> </li> <li typeof="foaf:Person"> <a property="foaf:name" rel="foaf:homepage" href="http://example.com/eve">Eve</a> </li> <li typeof="foaf:Person"> <a property="foaf:name" rel="foaf:homepage" href="http://example.com/manu">Manu</a> </li> </ul></div> Hideaki Takeda / National Institute of Informatics
  • 67. Using RDFa• RDF Validator – http://validator.w3.org/• RDF Distiller – http://www.w3.org/2007/08/pyRdfa/ Hideaki Takeda / National Institute of Informatics
  • 68. <?xml version="1.0" encoding="UTF-8"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN" "http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd"><html xmlns="http://www.w3.org/1999/xhtml" xmlns:foaf="http://xmlns.com/foaf/0.1/" <body about="http://example.org/john-d/#me"> xmlns:dc="http://purl.org/dc/elements/1.1/" <h1>Johns Home Page</h1> version="XHTML+RDFa 1.0" xml:lang="en"> <p>My name is <span property="foaf:nick">John D</span> <head> and I like <title>Johns Home Page</title> <a href="http://www.neubauten.org/" rel="foaf:interest" <base href="http://example.org/john-d/" /> xml:lang="de">Einsturzende Neubauten</a>. <meta property="dc:creator" content="Jonathan Doe" /> </p> <link rel="foaf:primaryTopic" <p> href="http://example.org/john-d/#me" /> My <span rel="foaf:interest" </head> resource="urn:ISBN:0752820907">favorite book is the inspiring <span about="urn:ISBN:0752820907"> <cite property="dc:title">Weaving the Web</cite> by <span property="dc:creator">Tim Berners-Lee</span></span> </span> </p> </body> </html> <http://example.org/john-d/> <http://xmlns.com/foaf/0.1/primaryTopic> <http://example.org/john- d/#me>. <http://example.org/john-d/> <http://purl.org/dc/elements/1.1/creator> "Jonathan Doe"@en. <http://example.org/john-d/#me> <http://xmlns.com/foaf/0.1/nick> "John D"@en. <http://example.org/john-d/#me> <http://xmlns.com/foaf/0.1/interest> <http://www.neubauten.org/>. <http://example.org/john-d/#me> <http://xmlns.com/foaf/0.1/interest> <urn:ISBN:0752820907>. <urn:ISBN:0752820907> <http://purl.org/dc/elements/1.1/title> "Weaving the Web"@en. <urn:ISBN:0752820907> <http://purl.org/dc/elements/1.1/creator> "Tim Berners-Lee"@en. Hideaki Takeda / National Institute of Informatics
  • 69. Summary• Linked Data is the practical application of Semantic Web – The bottom-up approach – Postpone the ontology issue• A technological solution for data sharing – Data science – Open Government Hideaki Takeda / National Institute of Informatics