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2012 INTERNATIONAL ASIAN SUMMER SCHOOL IN LINKED DATA  IASLOD 2012, August 13-17 , 2012, KAIST, Daejeon , Korea. General Introduction for Semantic Web and Linked Open Data. Hideaki Takeda National Institute of Informatics takeda @ nii.ac.jp. Semantic Web and Linked Data.

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general introduction for semantic web and linked open data

2012 INTERNATIONALASIAN SUMMER SCHOOL IN LINKED DATA 

IASLOD 2012, August 13-17, 2012, KAIST, Daejeon, Korea

General Introduction for Semantic Web and Linked Open Data

Hideaki Takeda

National Institute of Informatics

takeda@nii.ac.jp

semantic web and linked data
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
the aim of the semantic web
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/

semantic web1

Automation

Integration

Re-use of data

自動化

統合

データの再利用

Semantic Web
  • Realization of various information exchanging via Web
next generation web
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

a brief introduction of xml
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>

slide8
XML
  • XML(eXtensible Markup Language)
    • Can define original tags
    • Represent logical structures of data
      • DTD
    • Do not include style information
      • XST

<lecturelist>

<lecture>

<title id=1234> Knowledge Sharing Systems</title>

<lecturer> Hideaki Takeda</lecturer>

<schedule>

<week>Wednesday</week>

<time>3rd</time>

</lecture>

...

</lecturelist>

whey is xml not sufficient
Whey is XML not sufficient?

<person>

<name> Hideaki Takeda</name>

<age> 20</age>

</person>

<個人>

<名前>Hideaki Takeda</名前>

<年齢> 20</年齢>

</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
architecture for the semantic web
Architecture for the Semantic Web

Tim Berners-Leehttp://www.w3.org/2002/Talks/09-lcs-sweb-tbl/

how to describe meaning
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)
metadata
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 object's 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.

metadata1
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

a layer model for semantic web
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-Leehttp://www.w3.org/2002/Talks/09-lcs-sweb-tbl/

rdf resource description framework
RDF (Resource Description Framework)
  • A framework to describe metadata
  • Separation of model and syntax
  • W3C Recommendation (2004)
rdf model
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
rdf model1
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”

http://www-kasm.nii.ac.jp/~takeda

Creator

“Hideaki Takeda”

Resource

Property

Value

rdf model2
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” .

http://www-kasm.nii.ac.jp/~takeda

Creator

http://www.nii.ac.jp/staffid/123456

name

email

“Hideaki Takeda”

“takeda@nii.ac.jp”

rdf model3
RDF model
  • Creator of http://www-kasm.nii.ac.jp/~takeda has name “Hideaki Takeda” email “takeda@nii.ac.jp” .

http://www-kasm.nii.ac.jp/~takeda

Creator

name

email

“Hideaki Takeda”

“takeda@nii.ac.jp”

rdf syntax
RDF syntax
  • Creator of http://www-kasm.nii.ac.jp/~takeda is “Hideaki Takeda”

http://www-kasm.nii.ac.jp/~takeda

Creator

“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>

rdfs rdf schema
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
slide22
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:domain

RDFSStructure by RDF

Resource Description Framework(RDF) Schema Specification 1.0

http://www.w3.org/TR/2000/CR-rdf-schema-20000327/

rdf schema
RDF Schema
  • Range
    • Only one
      • No cardinality
  • Domain
    • Multiple (or)
  • rdfs:Class
  • rdfs:SubclassOf
    • Detailed class
    • Multiple
    • Transivity
  • rdf:type
    • Indicate an instance of a class
  • rdf:property
    • Attribute
  • rdfs:subPropertyOf
    • Detailed property
    • Transivity
rdf schema1

Animal

RDF Schema

“The class of person”

s

rdfs:comment

Person

d

d

maritalStatus

d

ssn

<rdf:RDFxml:lang="en"

xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"

xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">

<rdfs:Classrdf:ID="Person">

<rdfs:comment>The class of people.</rdfs:comment>

<rdfs:subClassOfrdf:resource="http://www.w3.org/

2000/03/example/

classes#Animal"/>

</rdfs:Class>

<rdf:Property ID="maritalStatus">

<rdfs:rangerdf:resource="#MaritalStatus"/>

<rdfs:domainrdf:resource="#Person"/>

</rdf:Property>

<rdf:Property ID="ssn">

<rdfs:comment>Social Security Number</rdfs:comment>

<rdfs:rangerdf:resource="http://www.w3.org/2000/03/example/classes#Integer"/>

<rdfs:domainrdf:resource="#Person"/>

</rdf:Property>

<rdf:Property ID="age">

<rdfs:rangerdf:resource="http://www.w3.org/2000/03/example/classes#Integer"/>

<rdfs:domainrdf:resource="#Person"/>

</rdf:Property>

<rdfs:Classrdf:ID="MaritalStatus"/>

<MaritalStatusrdf:ID="Married"/>

<MaritalStatusrdf:ID="Divorced"/>

<MaritalStatusrdf:ID="Single"/>

<MaritalStatusrdf:ID="Widowed"/>

</rdf:RDF>

r

age

MaritalStatus

r

rdfs:comment

Integer

t

t

Married

Single

“Social Security Number”

t

Windowed

t = rdf:type

d = rdfs:domain

r = rdfs:range

= class

= class instance

= property

t

Divorced

Resource Description Framework(RDF) Schema Specification 1.0

http://www.w3.org/TR/2000/CR-rdf-schema-20000327/

owl web ontology language
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
linked data1
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
linked data2
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
architecture for the semantic web1
Architecture for the Semantic Web
  • The world of classes (Ontologies)
  • The world of instances (Linked Data)

Tim Berners-Leehttp://www.w3.org/2002/Talks/09-lcs-sweb-tbl/

layers of semantic web
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-Leehttp://www.w3.org/2002/Talks/09-lcs-sweb-tbl/

layers of semantic web1
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 LinkedData
      • Difficult to describe complex structures
      • Still need for class description (-> ontology)

Descriptions on classes

Ontology

Description on instances

Linked Data

Tim Berners-Leehttp://www.w3.org/2002/Talks/09-lcs-sweb-tbl/

linked data3
Linked Data
    • Linked Datais“Web of Data”
    • Data published as RDF
    • Can refer from outside
  • The four rules for Linked Data
linked data4
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

linked data5
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
linking open data lod
Linking Open Data (LOD)
  • The project to collect published Linked Data
  • Major Linked Data
  • (Translated from the original resources)
    • Dbpedia (Wikipedia) 270Million 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
linked data6
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
how to use linked data
How to use Linked Data

Linked Data Browser

Linked Data Mashup

Linked Data Search Engine

Things

Things

Things

Things

Things

linked data7
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
linked data browser
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
linked data8
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
linked data search engine
Linked Data Search Engine
  • Search RDF data with crawled data set
    • Swoogle
    • Sindice
    • watson
linked data9
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
how to use linked data1
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/
bio2rdf
Bio2RDF
  • Search LOD in bioscience
  • Translate data into RDFif not
linked data10
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
slide60
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
principles of rdfa
Principles of RDFa
  • RDF contents are defined through XML attributes (no elements)
  • XML/HTML tree structure is used
  • Varios attributes are defined by RDFa
    • Some attributes (@href, @rel) are also reused
  • The text content can be also reused
examples
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" .

slide63

<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">Jo's Barbecue</h2>

<h3 property="dc:creator">Eve</h3>

...

</div>

...

</div>

slide64

<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">

<imgsrc="http://example.com/bob/photos/sunset.jpg" />

<span property="dc:title">Beautiful Sunset</span>

by

<span property="dc:creator">Bob</span>.

</div>

</div>

slide65

<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>

slide66

<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>

using rdfa
Using RDFa
  • RDF Validator
    • http://validator.w3.org/
  • RDF Distiller
    • http://www.w3.org/2007/08/pyRdfa/
slide68

<?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/"

xmlns:dc="http://purl.org/dc/elements/1.1/"

version="XHTML+RDFa 1.0" xml:lang="en">

<head>

<title>John's Home Page</title>

<base href="http://example.org/john-d/" />

<meta property="dc:creator" content="Jonathan Doe" />

<link rel="foaf:primaryTopic"

href="http://example.org/john-d/#me" />

</head>

<body about="http://example.org/john-d/#me">

<h1>John's Home Page</h1>

<p>My name is <span property="foaf:nick">John D</span>

and I like

<a href="http://www.neubauten.org/" rel="foaf:interest"

xml:lang="de">EinsturzendeNeubauten</a>.

</p>

<p>

My <span rel="foaf:interest" 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.

summary
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