Semantic Web and Linked Open Data Hideaki Takeda National Institute of Informatics takeda niiacjp 2012 INTERNATIONAL ASIAN SUMMER SCHOOL IN LINKED DATA IASLOD 2012 August 1317 ID: 648939
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Slide1
General Introduction for Semantic Web and Linked Open Data
Hideaki TakedaNational Institute of Informaticstakeda＠nii.ac.jp
2012 INTERNATIONAL
ASIAN
SUMMER SCHOOL IN LINKED DATA
IASLOD
2012, August 13-17
, 2012, KAIST,
Daejeon
,
KoreaSlide2
Semantic Web and Linked DataSemantic WebWhat is Semantic Web
How to realize Semantic WebMetadataRDFRDFSOWLLinked 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
SPARQLSlide3
Semantic WebSlide4
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/Slide5
Semantic Web
Realization of various information exchanging via Web
自動化
統合
データの再利用
Automation
Integration
Re-use of dataSlide6
Next Generation Web?Evolution of WebHTML: Web for DisplayXML: Web with Syntax?? : Web with
SemanticsWhy should we embed semantics into Web? FromWeb for Human To
Web for human and machines
cf. Web for machinesSlide7
A brief introduction of XMLLimitation of HTMLChaos by mixture of displaying and text structurese.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 Structuree.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
XMLXML(eXtensible Markup Language)Can define original tagsRepresent logical structures of data
DTDDo not include style informationXST
<
lecturelist
>
<lecture>
<title id=1234> Knowledge Sharing Systems</title>
<lecturer> Hideaki Takeda</lecturer>
<schedule>
<week>Wednesday</week>
<time>3rd</time>
</lecture>
...
</
lecturelist
>Slide9
Whey is XML not sufficient?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
<person>
<name> Hideaki Takeda</name>
<age> 20</age>
</person>
<
個人
>
<
名前
>Hideaki Takeda</
名前
>
<
年齢
> 20</
年齢
>
</
個人
>Slide10
Architecture for the Semantic Web
Tim Berners-Lee
http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/Slide11
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 dataNeed to architecture for common understandingSyntax (language or scheme)Vocabulary (ontology)Slide12
MetadataWhat is metadata?Data about data
What one can say about any information objectWhat 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.Slide13
MetadataMetadata to individual information objectsBibliography，
Dublin CoreMetadata to part or structure of information objectsDrawings，RDF，RDFS, OWL
Type
：
tractor
Owner
：
Taro
Product year
：
2002
Axis:
Connect body to wheel
Wheel
BodySlide14
A Layer model for Semantic Web
RDF (Resource Description Framework)The most primitive model for metadata descriptionSVO 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/Slide15
RDF (Resource Description Framework)A framework to describe metadataSeparation of model and syntaxW3C Recommendation (2004)Slide16
RDF ModelElementResource: URI(Universal Resource Identifier)Literal(string)No need to be specified by Web
Property: Attribute when describing resourcesURI or Literal just as ResourceStatement: triad of resource, property, and resourceSlide17
RDF modelStatementCreator 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
“Hideaki Takeda”
Creator
Resource
Property
ValueSlide18
RDF modelCreator 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
“Hideaki Takeda”
Creator
http://www.nii.ac.jp/staffid/123456
“takeda@nii.ac.jp”
name
emailSlide19
RDF modelCreator of http://www-kasm.nii.ac.jp/~takeda has name “Hideaki Takeda” email “takeda@nii.ac.jp” ．
http://www-kasm.nii.ac.jp/~takeda
“Hideaki Takeda”
Creator
“takeda@nii.ac.jp”
name
emailSlide20
RDF syntaxCreator of http://www-kasm.nii.ac.jp/~takeda is “Hideaki Takeda”
http://www-kasm.nii.ac.jp/~takeda
“Hideaki Takeda”
Creator
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> Slide21
RDFS (RDF Schema)Stronger knowledge representation modelRDF: ER model，semantic net
RDF Schema: Frame model，object-oriented paradigmMinimal definitionProperty-centered approach
RDFS is defined as extension of RDF
RDFS gives definitions of RDF descriptionsSlide22
RDFSClass Definitionrdfs:Resource
rdfs:Classrdf:Propertyrdfs:ConstraintPropertyrdfs:Literal
Property Definition
rdf:type
rdfs:subClassOf
rdfs:subPropertyOf
rdfs:comment
rdfs:label
rdfs:seeAlso
rdfs:isDefinedBy
ConstraintProperty Definition
rdfs:range
rdfs:domain
Resource Description Framework(RDF) Schema Specification 1.0
http://www.w3.org/TR/2000/CR-rdf-schema-20000327/
RDFS
Structure by RDFSlide23
RDF Schemardfs:Classrdfs:SubclassOf
Detailed classMultipleTransivityrdf:typeIndicate an instance of a class
rdf:property
Attribute
rdfs:subPropertyOf
Detailed property
Transivity
Range
Only one
No cardinality
Domain
Multiple (or)Slide24
RDF Schema
<rdf:RDF xml: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:Class
rdf:ID
="
Person
">
<
rdfs:comment
>The class of people.</
rdfs:comment
>
<
rdfs:subClassOf
rdf:resource="http://www.w3.org/
2000/03/example/
classes#Animal
"/></rdfs:Class
><
rdf:Property ID="maritalStatus
">
<rdfs:range rdf:resource="#MaritalStatus"/> <rdfs:domain rdf:resource="#Person"/></
rdf:Property><rdf:Property ID="ssn
"> <rdfs:comment>Social Security Number</rdfs:comment>
<rdfs:range rdf:resource="http://www.w3.org/2000/03/example/classes#
Integer"/> <rdfs:domain rdf:resource
="#Person"/></rdf:Property><rdf:Property ID="
age"> <rdfs:range
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"/><MaritalStatus
rdf:ID="Single"/><
MaritalStatus rdf:ID="Widowed"/></rdf:RDF
>Animal
Personssn
agemaritalStatus
sd
MaritalStatus
r“The class of person”
rdfs:commentIntegerd
rd
“Social Security Number”rdfs:comment
t = rdf:typed = rdfs:domainr = rdfs:range = class = class instance = property
Resource Description Framework(RDF) Schema Specification 1.0http://www.w3.org/TR/2000/CR-rdf-schema-20000327/
MarriedDivorced
Single
Windowed
t
tttSlide25
OWL(Web Ontology Language)More general knowledge representationBased on Description LogicsFeaturesClass
Necessary condition / necessary and sufficient conditionClass expression:Constraint by property Like slot definition of a classType constraint (all/some), cardinality, typed cardinalityLogical operation of classes: union, intersection, negation
Property
Multiple ranges and domains
Specifying meta-property
Import of definitionsSlide26
Linked DataSlide27
Linked DataWhat is Linked Data?The State-of-the-Art of Linked DataLinking Open Data (LOD)
How to use Linked DataLinked Data BrowserLinked Data Search EngineLinked Data ApplicationsHow to use RDF
RDFa
SPARQLSlide28
Linked DataWhat is Linked Data?The State-of-the-Art of Linked Data
Linking Open Data (LOD)How to use Linked DataLinked Data BrowserLinked Data Search EngineLinked Data ApplicationsHow to use RDF
RDFa
SPARQLSlide29
Architecture for the Semantic Web
Tim Berners-Lee http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/
The world of instances
(Linked
Data)
The
world of classes (
Ontologies
)Slide30
Layers of Semantic Web
OntologyDescriptions on classesRDFS, OWL
Challenges for ontology building
Ontology building is difficult by nature
Consistency, comprehensiveness, logicality
Alignment of ontologies is more difficult
Tim Berners-Lee
http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/
Descriptions on classes
インスタンスに関する記述
Ontology
Linked DataSlide31
Layers of Semantic Web
Linked DataDescriptions 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)
Tim Berners-Lee
http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/
Descriptions on classes
Description
on instances
Ontology
Linked DataSlide32
Linked DataLinked Data
is “Web of Data”Data published as RDFCan refer from outsideThe four rules for Linked DataSlide33
Linked DataThe four rules for Linked DataUse 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 URNWhen 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.htmlSlide34
Linked DataWhat is Linked Data?The State-of-the-Art of Linked Data
Linking Open Data (LOD)How to use Linked DataLinked Data BrowserLinked Data Search EngineLinked Data ApplicationsHow to use RDF
RDFa
SPARQLSlide35
Linking Open Data (LOD)The project to collect published Linked DataMajor Linked Data(Translated from the original resources)
Dbpedia (Wikipedia) 270 Million TriplesGeonames
：
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 WrapperSlide36Slide37Slide38
LOD Cloud(Linking Open Data)Slide39
http://dbpedia.org/page/TokyoSlide40
http://en.wikipedia.org/wiki/TokyoSlide41Slide42Slide43
Linked DataWhat is Linked Data?The State-of-the-Art of Linked DataLinking Open Data (LOD)
How to use Linked DataLinked Data BrowserLinked Data Search EngineLinked Data ApplicationsHow to use RDF
RDFa
SPARQLSlide44
How to use Linked Data
Things
Things
Things
Things
Things
Linked
Data
Browser
Linked
Data
Mashup
Linked
Data
Search EngineSlide45
Linked DataWhat is Linked Data?The State-of-the-Art of Linked DataLinking Open Data (LOD)
How to use Linked DataLinked Data BrowserLinked Data Search EngineLinked Data ApplicationsHow to use RDF
RDFa
SPARQLSlide46
Linked Data BrowserBrowse linked data just as browsing web pagesShow RDF data
Prompt links to followSystem/ServiceMablesDisplay data by following linksTabulator
Firefox plugin
/
online
Adding information in a single page
Sig.ma
Showing RDF resources which can be operatedSlide47Slide48
TabulatorSlide49Slide50
Linked DataWhat is Linked Data?The State-of-the-Art of Linked DataLinking Open Data (LOD)
How to use Linked DataLinked Data BrowserLinked Data Search EngineLinked Data ApplicationsHow to use RDF
RDFa
SPARQLSlide51
Linked Data Search EngineSearch RDF data with crawled data setSwoogle
SindicewatsonSlide52
http://sindice.com/Slide53Slide54
Linked DataWhat is Linked Data?The State-of-the-Art of Linked DataLinking Open Data (LOD)
How to use Linked DataLinked Data BrowserLinked Data Search EngineLinked Data ApplicationsHow to use RDF
RDFa
SPARQLSlide55
How to use Linked DataSemantic Data Mash-up ApplicationsSemaPlorer
http://btc.isweb.uni-koblenz.de/Dbpedia Mobilehttp://wiki.dbpedia.org/DBpediaMobile
Bio2RDF
http://bio2rdf.org/Slide56
DBpedia MobileSlide57
Bio2RDF
Search LOD in bioscienceTranslate data into RDF if notSlide58
Bio2RDFSlide59
Linked DataWhat is Linked Data?The State-of-the-Art of Linked DataLinking Open Data (LOD)
How to use Linked DataLinked Data BrowserLinked Data Search EngineLinked Data ApplicationsHow to use RDF
RDFa
SPARQLSlide60
RDFaAdd 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 resourcesSlide61
Principles of RDFaRDF contents are defined through XML attributes (no elements
)XML/HTML tree structure is usedVarios attributes are
defined
by
RDFa
S
ome
attributes (@
href
, @
rel
) are also reused
T
he
text content
can be also reusedSlide62
Examples
<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>
http://example.com/alice/posts/trouble_with_bob
<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" .
In N3Slide63
<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
"
>
<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>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>Slide67
Using RDFaRDF Validatorhttp://validator.w3.org
/RDF Distillerhttp://www.w3.org/2007/08/pyRdfa/Slide68
<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
.
<?
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">Einsturzende Neubauten</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>Slide69
SummaryLinked Data is the practical application of Semantic WebThe bottom-up approach Postpone the ontology issue
A technological solution for data sharing Data scienceOpen Government