Linked Data Technology and Status

Linked Data
Technology & Status

Dr. Myungjin Lee

Linked Data & Semantic Web Technology

The Semantic Web

more vocabulary
for describing properties and classes

a vocabulary for describing
properties and classes to exchange rules
of RDF-based resources between many "rules languages"

a protocol and query language
for semantic web data sources
an elemental syntax
for content structure
within documents

a simple language
for expressing data models,
which refer to objects ("resources")
and their relationships
a string of characters used to identify a name or a resource

Linked Data & Semantic Web Technology http://www.w3.org/2007/Talks/0130-sb-W3CTechSemWeb/#(24)

What is Linked Data?
Linked data describes a method of publishing structured
data so that it can be interlinked and become more useful.

The Semantic Web isn't just about
putting data on the web. It is about
making links, so that a person or
machine can explore the web of data.
With linked data, when you have some of
it, you can find other, related, data.
- A roadmap to the Semantic Web by Tim Berners-Lee

Linked Data & Semantic Web Technology http://www.w3.org/DesignIssues/LinkedData.html

Four Principles of Linked Data
1. Use URIs to identify things.

2. Use HTTP URIs so that these things can be referred
to and looked up ("dereferenced") by people and user
agents.

3. Provide useful information about the thing when its
URI is dereferenced, using standard formats such as
RDF/XML.

4. Include links to other, related URIs in the exposed
data to improve discovery of other related
information on the Web.


5 Star Linked Data

★ Available on the web (whatever format) but with an
open licence, to be Open Data

★★ Available as machine-readable structured data (e.g.
excel instead of image scan of a table)

★★★ as (2) plus non-proprietary format (e.g. CSV instead
of excel)

★★★★ All the above plus, Use open standards from W3C
(RDF and SPARQL) to identify things, so that people
can point at your stuff
★★★★★ All the above, plus: Link your data to other people’s
data to provide context


The Basic Requirements for Linked Data

a vocabulary for describing
properties and classes
of RDF-based resources

a protocol and query language
for semantic web data sources
an elemental syntax
for content structure
within documents

a simple language
for expressing data models,
which refer to objects ("resources")
and their relationships
a string of characters used to identify a name or a resource


Linked Data & Semantic Web Technology http://www.google.co.kr/search?q=namdeamun

URI, Thing, and Representation
looks up
URI
Person http://data.kdata.kr/resource/Namdaemun
Machine
refers

URI
http://data.kdata.kr/resource/Sungnyemun
links identifies
and
names
URI
Thing
http://dbpedia.org/resource/Namdaemun

represents

Representation
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>Namdaemun | kdata.kr</title>
<link rel="alternate" type="application/rdf+xml" href="http://data.kdata.kr/data/Namdaemun" title="RDF" />
</head>
<body onLoad="init();">
<div id="header">
<div>
<h1 id="title">Namdaemun</h1>
<div id="homelink">  at <a href="http://kdata.kr">kdata.kr</a>

Linked Data & Semantic Web Technology http://www.slideshare.net/lysander07/open-hpi-semweb02part1

Linked Data & Semantic Web Technology http://www.w3.org/TR/cooluris/

URIs for Real-World Objects
• Be on the Web
– Given only a URI, machines and people should be
able to retrieve a description about the resource
identified by the URI from the Web.

• Be unambiguous
– There should be no confusion between identifiers for
Web documents and identifiers for other resources.


URIs for Real-World Objects

<URI-of-alice> a foaf:Person;
foaf:name "Alice";
foaf:mbox <mailto:alice@example.com>;
foaf:homepage <http://www.example.com/people/alice> .

Resource identifier (URI)

ID

for semantic web applications for web browsers

RDF HTML

RDF document URI HTML document URI


Distinguishing between Representations and Descriptions
http://data.kdata.kr/resource/Namdaemun

Thing

303 redirect

http://data.kdata.kr/page/Namdaemun

Generic
Document

application/rdf+xml content text/html
negotiation

RDF HTML

http://data.kdata.kr/page/Namdaemun.rdf http://data.kdata.kr/page/Namdaemun.html


Cool URIs
• Simplicity
– short and mnemonic

• Stability
– remain as long as possible

• Manageability
– issue your URIs in a way that you can manage


Designing URI Sets for the UK Public Sector
• URIs:
– name the set and describe its characteristics
– identify for the real-world ‘Things’ in a single
concept
– provide a means of looking up data on the web
– provide mechanisms to:
• lookup an Identifier URI and be redirected to its Document
URI
• discover and get each of the Representation URIs

URI Type URI structure Examples

Identifier http://{domain}/id/{concept}/{reference} http://education.data.gov.uk/id/school/78

https://www.gov.uk/government/publications/designing-uri-sets-for-the-uk-public-sector
Linked Data & Semantic Web Technology http://data.gov.uk/resources/uris

URI Design Principles:
Creating Unique URIs for Government Linked Data
• URI Template:

'http://' BASE '/' 'id' '/' ORG '/' CATEGORY ( '/' TOKEN )+

• States and Territories
– Owner
• federal
– Suggested
• http://BASE/id/us/state/NAME
– Example
• http://logd.tw.rpi.edu/id/us/state/Vermont

Linked Data & Semantic Web Technology http://logd.tw.rpi.edu/instance-hub-uri-design

XML (Extensible Markup Language)
• a textual data format for the representation of
arbitrary data structures over the Internet
• both human-readable and machine-readable

<title>
W3C Demonstrates … title title
</title>
<date> date date
12 February 2013
</date> body
<body> body
W3C invites media,
analysts, and other attendees
of Mobile World Congress
bold1 bold1
…
bold2
</body>
bold2

Concept Content Structure Presentation

Related XML DTD XSLT
Recommendations XML Schema XSL-fo
XPath

Linked Data & Semantic Web Technology http://en.wikipedia.org/wiki/Xml

Data Representation of XML
• Various ways to represent data using XML
– Myungjin Lee is Hye-jin’s husband.
<conjugalrelation>
<husband>Myungjin Lee</husband>
<wife>Hye-jin Han</wife>
</conjugalrelation>

<conjugalrelation husband=“Myungjin Lee”>
<wife>Hye-jin Han</wife>
</conjugalrelation>

<conjugalrelation husband=“Myungjin Lee” wife=“Hye-jin Han” />

• We need a method to represent data on abstract
level.


RDF (Resource Description Framework)
• a general method for conceptual description or
modeling of information that is implemented in
web resources, using a variety of syntax formats

– Myungjin Lee is Hye-jin’s husband.

hasWife

Linked Data & Semantic Web Technology http://en.wikipedia.org/wiki/Resource_Description_Framework

Data Representation of RDF

hasWife

http://semantics.kr/rel/hasWife
http://semantics.kr/myungjinlee http://semantics.kr/hye-jinhan

Subject Predicate Object
URI reference URI reference URI reference or Literal

Triple


RDF Example
http://www.cars.com/car#Gasoline

http://www.cars.com/car#fuel

http://www.cars.com/car#AWD http://www.cars.com/car#GDI

http://www.cars.com/car#drivetrain http://www.cars.com/car#engine

http://www.cars.com/car#doors http://www.cars.com/car#wheelbase

4 http://www.cars.com/car#A6 115”

http://www.cars.com/car#body_style http://www.cars.com/car#transmission

http://www.cars.com/car#Sedan http://www.cars.com/car#Auto_8-Speed

http://www.w3.org/1999/02/22-rdf-syntax-ns#type

http://www.cars.com/car#Car


RDF Serialization
• N-Triples
– RDF Test Cases, W3C Recommendation, 10 February 2004
– a line-based, plain text serialization format for storing and transmitting
RDF data

• Notation 3 (N3)
– a shorthand non-XML serialization of RDF models, designed with human-
readability in mind
– much more compact and readable than XML RDF notation

• Turtle (Terse RDF Triple Language)
– W3C Candidate Recommendation, 19 February 2013
– a format for expressing data in the Resource Description Framework (RDF)
data model
– a subset of Notation3 (N3) language, and a superset of the minimal N-
Triples format

• RDF/XML
– W3C Recommendation, 10 February 2004
– an XML syntax for writing down and exchanging RDF graphs
http://en.wikipedia.org/wiki/N-Triples
http://en.wikipedia.org/wiki/Notation3
Linked Data & Semantic Web Technology http://en.wikipedia.org/wiki/Turtle_(syntax)

N-Triple
<http://en.wikipedia.org/wiki/Tony_Benn> <http://purl.org/dc/elements/1.1/title> "Tony Benn" .
<http://en.wikipedia.org/wiki/Tony_Benn> <http://purl.org/dc/elements/1.1/publisher> "Wikipedia" .

N3
@prefix dc: <http://purl.org/dc/elements/1.1/>.

<http://en.wikipedia.org/wiki/Tony_Benn> dc:title "Tony Benn";
dc:publisher "Wikipedia".

RDF/XML
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:dc="http://purl.org/dc/elements/1.1/">
<rdf:Description rdf:about="http://en.wikipedia.org/wiki/Tony_Benn">
<dc:title>Tony Benn</dc:title>
<dc:publisher>Wikipedia</dc:publisher>
</rdf:Description>
</rdf:RDF>

Turtle
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix dc: <http://purl.org/dc/elements/1.1/> .
@prefix ex: <http://example.org/stuff/1.0/> .

<http://www.w3.org/TR/rdf-syntax-grammar>
dc:title "RDF/XML Syntax Specification (Revised)" ;
ex:editor [ ex:fullname "Dave Beckett";
ex:homePage <http://purl.org/net/dajobe/>
] .


Linked Data & Semantic Web Technology http://www.w3.org/TR/rdf11-concepts/

RDF 1.0 vs RDF 1.1

RDF 1.0 RDF 1.1

IRI (Internationalized
Resource Identification URI
Resource Identifier)

Multiple RDF Graphs X O

HTML content for literal
X rdf:HTML
value


Recommendations of RDF

Linked Data & Semantic Web Technology http://www.w3.org/standards/techs/rdf#w3c_all

RDF Schema
• W3C Recommendation, 10 February 2004
• to define classes and properties that may be
used to describe classes, properties and other
resources

• RDF Schema allows
– Definition of Classes
– Definition of Properties and Restrictions
– Definition of Hierarchies

Linked Data & Semantic Web Technology http://www.slideshare.net/lysander07/openhpi-22

RDF Schema Example

TBox - terminological component
rdf:type car:Vehicle rdf:Property

rdfs:Class
rdfs:subClassOf rdf:type

rdf:type
car:Car car:body_style
rdfs:domain

rdf:type
rdfs:range

car:A6 car:Sedan car:Style
car:body_style rdf:type

ABox - assertion component


RDF Semantics
• to provide a formal meaning based on a model-
theoretic semantics in its abstract syntax

<x, y> is in IEXT(I(rdfs:subClassOf))
if and only if x and y are in IC
car:Vehicle
and ICEXT(x) is a subset of ICEXT(y)

rdfs:subClassOf

car:Car rdf:type

rdf:type

car:A6


SPARQL
• Why do we need a query language for RDF?
– Why de we need a query language for RDB?
– to get to the knowledge from RDF

• SPARQL Protocol and RDF Query Language
– to retrieve and manipulate data stored in Resource
Description Framework format
– to use SPARQL via HTTP

Linked Data & Semantic Web Technology http://www.slideshare.net/lysander07/openhpi-semweb03part1

SPARQL Example
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?email
WHERE {
?person a foaf:Person.
?person foaf:name ?name.
?person foaf:mbox ?email.
}

RDF Knowledge Base

?name ?email

Myungjin Lee mjlee@li-st.com

Gildong Hong gildong@daum.net

Grace Byun grace@naver.com


SPARQL Query Forms
• SELECT query
– Used to extract raw values from a SPARQL endpoint, the
results are returned in a table format.
• CONSTRUCT query
– Used to extract information from the SPARQL endpoint
and transform the results into valid RDF.
• ASK query
– Used to provide a simple True/False result for a query on
a SPARQL endpoint.
• DESCRIBE query
– Used to extract an RDF graph from the SPARQL
endpoint, the contents of which is left to the endpoint to
decide based on what the maintainer deems as useful
information.

Linked Data & Semantic Web Technology http://en.wikipedia.org/wiki/SPARQL

OWL (Web Ontology Language)
• knowledge representation languages for
authoring ontologies
• If you need more expressiveness  OWL
– such as,

Man ∩ Woman =Ø
descendant descendant
Person Person Person

Genre

descendant type

hasGenre
_01 Action
1:1
Husband Wife
subClassOf

ActionMovie


What more do we need?

SPARQL

Linked Data Platform

Linked Data Service

RDFa
HTML

+
RDBMS Triple Store HTML
HTML RDF
Knowledge
R2RML GRDDL


http://www.w3.org/TR/r2rml/

R2RML
• RDB to RDF Mapping Language
• W3C Recommendation 27 September 2012
• a language for expressing customized mappings
from relational databases to RDF datasets
RDB

R2RML
@prefix rr: <http://www.w3.org/ns/r2rml#>.
@prefix ex: <http://example.com/ns#>.

<#TriplesMap1>
rr:logicalTable [ rr:tableName "EMP" ];
rr:subjectMap [
rr:template "http://data.example.com/employee/{EMPNO}";
rr:class ex:Employee;
];
rr:predicateObjectMap [
rr:predicate ex:name;
rr:objectMap [ rr:column "ENAME" ];
].

Result
<http://data.example.com/employee/7369> rdf:type ex:Employee.
<http://data.example.com/employee/7369> ex:name "SMITH".

Linked Data Platform
• A set of best practices and simple approach for
a read-write Linked Data architecture, based on
HTTP access to web resources that describe
their state using RDF
• W3C Working Draft 25 October 2012

Linked Data & Semantic Web Technology http://www.w3.org/TR/ldp/

RDFa (the Resource Description Framework in attributes)

• W3C Recommendation, 07 June 2012
• to express machine-readable data in Web
documents like HTML, SVG, and XML
Example<p vocab="http://schema.org/" resource="#manu" typeof="Person">
My name is
<span property="name">Manu Sporny</span>
and you can give me a ring via
<span property="telephone">1-800-555-0199</span>.
<img property="image" src="http://manu.sporny.org/images/manu.png" />
</p>

Linked Data & Semantic Web Technology http://www.w3.org/TR/xhtml-rdfa-primer/

http://www.w3.org/TR/grddl/

GRDDL (Gleaning Resource Descriptions from Dialects of Languages)

• a mechanism and markup format for Gleaning
Resource Descriptions from Dialects of
Languages to obtain RDF triples out of XML
documents, including XHTML
HTML <html xmlns:grddl='http://www.w3.org/2003/g/data-view#'
grddl:transformation="glean_title.xsl getAuthor.xsl">
<head>
<title>Are You Experienced?</title>
</head>
... glean_title.xsl
<xsl:stylesheet version="1.0">
<xsl:template match="/">
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<rdf:Description rdf:about="{$subject}">
<dc:title>
<xsl:value-of select="/html:html/html:head/html:title"/>
</dc:title>
</rdf:Description>
</rdf:RDF>
</xsl:template>
</xsl:stylesheet>

RDF
<rdf:RDF>
<rdf:Description rdf:about="">
<dc:title>Are You Experienced?</dc:title>
</rdf:Description>
Linked Data & Semantic Web Technology </rdf:RDF>

Jena Platform

SPARQL
Fuseki

ARQ & LARQ
Linked Data Service

Jena API

HTML
HTML

TDB & SDB
Linked Data & Semantic Web Technology http://jena.apache.org/

Openlink Virtuoso
• a middleware and database engine hybrid that
combines the functionality of a traditional
RDBMS, ORDBMS, RDF, XML, etc.
– Relational Data Management
– RDF Data Management
– XML Data Management
– Free Text Content Management & Full Text
Indexing
– Document Web Server
– Linked Data Server
– Web Application Server
– Web Services Deployment (SOAP or REST)

Linked Data & Semantic Web Technology http://virtuoso.openlinksw.com/

Openlink Virtuoso Coverage

SPARQL
SPARQL Server

Linked Data Service

HTML
HTML

Sponger
Storage and Inference

http://lod-cloud.net/

The Linking Open Data cloud diagram


User Generated Content
Media

Publications
Government

Domain Number of datasets Triples (Out-)Links
Media 25 18,4185,2061 5044,0705
Geographic 31 61,4553,2484 3581,2328
Government 49 133,1500,9400 1934,3519
Publications 87 29,5072,0693 1,3992,5218
Cross-domain 41 41,8463,5715 6318,3065
Life Sciences 41 30,3633,6004 1,9184,4090
User-generated Content 20 1,3412,7413 344,9143
Total 295 316,3421,3770 5,0399,8829

Geographic

Life Sciences
Cross-Domain

Linked Data & Semantic Web Technology http://www.slideshare.net/lysander07/13-semantic-web-technologies-linked-data-semantic-search

KDATA (Linked Data for Korea)
Domain Triples
3,899
44,278
2,969
126,469
1,130
2,833
5,539
47,340
228,872
4,450
5,392
109,101
1,155
WiFi 1,671
KDATA 808
4,535
10,605
80,156
49,799
3,256
9,418
2,429
16,212
14,300
6,931
39,218
115,099
139,608
1,077,472
Linked Data & Semantic Web Technology http://kdata.kr/index.jsp

SPARQL
select ?s
where {
?s rdf:type <http://data.kdata.kr/class/NationalTreasure> .
?s rdfs:label "남대문" .
}
HTML

http://data.kdata.kr/resource/Namdaemun

<rdf:RDF>
<rdf:Description rdf:about="http://data.kdata.kr/data/Namdaemun?output=rdfxml">
<rdfs:label>RDF description of Namdaemun</rdfs:label>
<foaf:primaryTopic>
<kdc:StateDesignatedHeritage rdf:about="http://data.kdata.kr/resource/Namdaemun">
<rdfs:label>남대문</rdfs:label>
<rdfs:label>숭례문</rdfs:label>
<foaf:depiction rdf:resource="20060227132556895000.jpg"/>
<owl:sameAs rdf:resource="http://dbpedia.org/resource/Namdaemun"/>
...
</rdf:RDF>

RDF


Contents Search on the Semantic Web

Dr. Myungjin Lee
e-Mail : mjlee@li-st.com
Twitter : http://twitter.com/MyungjinLee
Facebook : http://www.facebook.com/mjinlee
SlideShare : http://www.slideshare.net/onlyjiny/

Linked Data Technology and Status

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