Linking Open Data
Linking the world of data
Iftikhar Alam
What is now
User generated content is growing
tremendously
Post Ajax era…
Blogs, wiki, comments, tags,
Isolated contents need deadly to get
connected.
An idea of Tim Berners-Lee (Semantic Web)
The world is connected, so do the data,
information and knowledge should be
connected.
Old terms
 Data
Structured format
Closed environment (Database: As a set)
Slow growth (in context of Database)
Display of results in any order is not an issue
Select * from students;
 Information
Un-structured format
Open environment (for every one), No
restriction on its contents
Order of result is important issue
Old terms….
 Knowledge – contextualizing information
 Comprehend the perceived information
 Add context (hp, core i7, ITB, 8GB RAM)…
 Context ultimately determines what’s actually what.
 Contextualization aids comprehension. For example, an
arithmetic problem may not seem very practical until it is seen
within a story problem; the real-life situation contextualizes the
math problem and makes it more understandable.
 Pythagoras's theorem
 a2+b2=c2
DBPedia..
Extract structured data from Wikipedia
Example Wasim Akram
Date of birth, name, matches etc.
Database to RDF
Apply SPARQL statements ..
1.PREFIX
plant: <http://www.linkeddatatools.com/plants>
2.FROM
<http://www.linkeddatatools.com/plantsdata/plants.r
df>
3.SELECT ?name WHERE {
4.?planttype plant:planttype ?name.
5.}
6.ORDER BY ?name
What is in our daily life
Access data
Manipulate data (add, delete, change)
Process data
Generate information (tables, forms)
Create knowledge (reports, papers..)
Data is our life
 Data is our daily bread
 Do we have identifier for data?
Not really important if data is small and individual (your
class we don’t needs roll numbers)
Really important if data is huge and connected
? Should we need identifier for our data
? Why do we need our name, or NIC number
? Can you refer to someone without identifier
?a person with good heart----
Make our busy life less messy
 We just got 24 hours per day, not more
 Add identifier to our data
Give the everyone-agreed-unique-identifier to each data
-- the perfect world of our dreamland
 We will not have any integration problem, most of the IT
departments can be closed
Different groups give different identifiers to the same
data – we can live with that, it is more real in our daily
life, standardization bodies and IT guys are helping
us (NIC is required for SIM Registration, but not as
roll number or registration number).
We are happy that we can refer to data
Where are our data
 In computer
 On the Web
 In my paper notes
 In printed books
…
Data are being digitalized and are available online
Web Data
Web data
 Data on the Web
 Online journal
 Blog
 Wiki
…
 Data in physical world
 Yourself
 Table
 Book in library
 Computer you are using
…
 The boundary is blurring
 Paper is both in your hand and on the Web
How to refer data
 Web data
 DOI (Digital Object Identifier)
 Alphnumeric strings, APA style starts with 10
 OpenID (Logging into other websites using facebook)
 URI (blog, wiki, homepage, …)
…
URI (Uniform Resource Identifier)
 To identify or name a resource on the Internet
 The main purpose is to enable interaction with
representations of the resource over a network,
typically WWW, using specific protocols

URN – like a person’s name
 urn:isbn:0-486-27557-4 – Book of “Romeo and Juliet”
URL – like a street address
 http://www.slis.indiana.edu
Linked Data
 A term coined by Tim Berners-Lee
 It describes HTTP-based Data Access by
Reference for the Web
 Current web is changing from hypertext links
(link documents) to hyperdata links (linking data)
Data are small components of the resources
It drills deep to the details of the resources
 Linked data provides a powerful mechanism for
meshing disparate and heterogeneous data
Vision from Sir Berners-Lee
 “The Semantic Web isn’t just about putting data on the
web. It is about making links”.
 Four Rules for linking data
 Use URIs as names for things
 Use HTTP URIs so that people can look up those names
 When someone looks up a URI, provide useful information
(URI dereferencing)
 Include links to other URIs, so that they can discover more
things
 “Breaking them does not destroy anything, but misses an
opportunity to make data interconnected. This in turn
limits the ways it can later be reused in unexpected
ways. It is the unexpected re-use of information which is
the value added by the web”
W3C SWEO Linking Open Data Project
Project aims to
 "The goal of the W3C SWEO Linking Open Data community project is to extend the
Web with a data commons by publishing various open datasets as RDF on the Web
and by setting RDF links between data items from different data sources."
Publish existing open license datasets as linked
data on the web
Interlink things between different data sources
Develop clients and applications that consume
linked data from the web
Bubbles in May 2007
Over 500M RDF triples
Around 120K RDF links between data sources
Bubbles in April 2008
>2B RDF triples
Around 3M RDF links
Bubble now
Semantic search engines
Use RDF
Sindice
Falcons (temporarily not available)
More on w3c website
Organization participating in the LOD
community
Academic
MIT, Univ Southampton, DERI, Open Univ,
Univ London, Univ Hannover, Penn State Univ,
Univ Leipzig, Univ Karlsruhe, Joanneum (AT),
Free Univ Berlin, Cyc, SouthEast Univ (CN), …
Commercial
BBC, OpenLink, Talis, Zitgist, Garlik, Mondeca,
Renault, Boad Interactive
What are Linked Data?
Linked Data require RDF
But not all RDF data are linked data
You have to compliant your RDF data
according to the four rules mentioned by
Berners-Lee
What is RDF?
Basic Ideas behind RDF
 RDF uses Web identifiers (URIs) to identify
resources
 RDF describes resources with properties and
property values
Everything can be represented as triples
 The essence of RDF is the (s,p,o) triple
Resource
(subject)
Property
(predicate)
Value
(object)
Subject has a property with value “object ” (s,p,o)
RDF Triples
 Triple
 A Resource (Subject) is anything that can have a URI: URIs
or blank nodes
 A Property (Predicate) is one of the features of the Resource:
URIs
 A Property value (Object) is the value of a Property, which
can be literal or another resource: URIs, literal, blank nodes
Resource
(subject)
Property
(predicate)
Value
(object)
Literals can be the object of an RDF statement, but cannot be the subject
or the predicate
Do you have linked data
 Linked data are just RDF triples
<rdf:Description about=“http://example.org/smith#albert”>
<fam:hasChild rdf:Resource="http://example.org/smith#brian">
<fam:hasChild rdf:Resource="http://example.org/smith#carol">
</rdf:Description>
 How can I get RDF triples
Relational database:
 D2R tools can convert them for you
RDFizers from SIMILE:
 Can convert JPEG, MARC/MODS, OAI-PMH, OCW(MIT
Open Course), Email, BibTex, Java, Javadoc, etc. to RDF
Thumb of the rules
Understand your data
What do you want to have in your data
Do not reinvent – REUSE!
Potential ontologies/vocabularies
• FOAF, SIOC, Geo
URI Aliases
Different URIs for the same non-information resource
(Berlin, etc.)
owl:sameAs to link these URI aliases
More principles
Linked Data is simply about using the Web
to create typed links between data from
different sources.
The principle of Linked data is to:
Use the RDF data model to publish structured
data on the web
Use RDF links to interlink data from different
data sources.
Use HTTP URIs to identify resource
To avoid other URI schemes (URNs or DOIs)
Power of Linked Data
rdf:type
ying
foaf:Person
dblp:publications
foaf:name
foaf:publication
Ying Ding
foaf:knows
Stefan
foaf:based_near
72K
dp:population
db:Galway
skos:subject
dp:Dublin
skos:subject
dp:Cities_in_Ireland
What LOD can bring?
 It will lift current document web up to a data web
 LOD browsers can let you navigate between
different data sources by following RDF links.
 It can drill down to the lower granularity of the
information
allowing you for more fine search on the web
making the question-answer search on the Web
possible
meshing up different data through RDF links
Making the built-on-top application easier
Document Web vs. Data Web
 Document Web
 Glued by hyperlinks
 Data are HTML pages
 Query result is HTML
pages, which can not be
further processed
 Data are just interlinked,
but not integrated
 Data access through
different APIs
 Data Web
 Glued by RDF links
 Data are RDF triples
 Query result is RDF
triples which can be easily
further processed (e.g.,
web services)
 Data are interlinked and
integrated, and links are
typed
 Data access through a
single and standardized
access mechanism
(maybe it will called in the
future LOD API?)
More about LOD
 LOD Wiki
 http://esw.w3.org/topic/SweoIG/TaskForces/CommunityProjects/Linking
OpenData
 Tutorial on how to publish LOD data
 http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/
 Further readings and tools
 W3C Track LOD WWW2008
 http://www.w3.org/2008/Talks/WWW2008-W3CTrack-LOD.pdf
 Linked Data Planet in New York 2008
 http://linkeddata.org/slides/2008-06-nyc-ldp.pdf
 LDOW2008 workshop in WWW2008
 http://sunsite.informatik.rwth-aachen.de/Publications/CEUR-WS/Vol369/
 ISWC 2008 LOD tutorial
 http://events.linkeddata.org/iswc2008tutorial
 LOD mailinglist