1. Linked Data
Technology & Status
Dr. Myungjin Lee
Linked Data & Semantic Web Technology
2. 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)
3. 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
4. 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.
Linked Data & Semantic Web Technology http://www.w3.org/DesignIssues/LinkedData.html
5. 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
Linked Data & Semantic Web Technology http://www.w3.org/DesignIssues/LinkedData.html
6. 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
7. Linked Data & Semantic Web Technology http://www.google.co.kr/search?q=namdeamun
8. 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
9. Linked Data & Semantic Web Technology http://www.w3.org/TR/cooluris/
10. 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.
Linked Data & Semantic Web Technology http://www.w3.org/TR/cooluris/
11. 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
Linked Data & Semantic Web Technology http://www.w3.org/TR/cooluris/
12. 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
Linked Data & Semantic Web Technology
13. Cool URIs
• Simplicity
– short and mnemonic
• Stability
– remain as long as possible
• Manageability
– issue your URIs in a way that you can manage
Linked Data & Semantic Web Technology http://www.w3.org/TR/cooluris/
14. 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
15. 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
16. 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
17. 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.
Linked Data & Semantic Web Technology
18. 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
19. 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
Linked Data & Semantic Web Technology
20. 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
Linked Data & Semantic Web Technology
21. 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)
23. Linked Data & Semantic Web Technology http://www.w3.org/TR/rdf11-concepts/
24. 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
Linked Data & Semantic Web Technology
26. 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
28. 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
Linked Data & Semantic Web Technology
29. 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
30. 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
Linked Data & Semantic Web Technology
31. 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
32. 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
Linked Data & Semantic Web Technology
33. What more do we need?
SPARQL
Linked Data Platform
Linked Data Service
RDFa
HTML
+
RDBMS Triple Store HTML
HTML RDF
Knowledge
R2RML GRDDL
Linked Data & Semantic Web Technology
34. 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 & Semantic Web Technology
35. 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/
36. 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/
37. 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>
38. Jena Platform
SPARQL
Fuseki
ARQ & LARQ
Linked Data Service
Jena API
RDBMS Triple Store HTML
HTML
HTML
TDB & SDB
Linked Data & Semantic Web Technology http://jena.apache.org/
39. 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/
40. Openlink Virtuoso Coverage
SPARQL
SPARQL Server
Linked Data Service
RDBMS Triple Store HTML
HTML
HTML
Sponger
Storage and Inference
Linked Data & Semantic Web Technology
42. 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
44. 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
Linked Data & Semantic Web Technology
45. 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/
