WTF is the Semantic Web and Linked Data

WTF is the Semantic Web and
Linked Data
Juan F. Sequeda
Department of Computer Science
University of Texas at Austin
Nov 17, 2011

Semantic Web? Linked Data?

WTF?

What is the Web?

“… the Web, is a system of
interlinked hypertext documents
accessed via the Internet. With a
web browser, one can view web
pages that may contain text,
images […] and navigate between
them via hyperlinks”
http://en.wikipedia.org/wiki/World_Wide_Web

Current Web = internet + links + docs

History of the Web
• Created by Tim Berners-Lee at CERN in 1989
• Mosaic browser in 1993
• W3C created in 1994
• Exponential growth mid 90s
• Amazon, Ebay – 1995
• Search engines – Google 1998
• Dot-com boom 1997 – 2001
• Web 2.0 – blogs, Facebook, Twitter, etc

WHAT’S THE
WEATHER IN
AUSTIN TODAY?

http://www.flickr.com/photos/jamieca/31631256/

What is the problem?
• The web is full of documents
• We aren’t always interested in documents
– We are interested in THINGS
– These THINGS might be in documents
• We can read a HTML document rendered in a
browser and find what we are searching for
– This is hard for computers.
– Computers have to guess (even though they are
pretty good at it)

The Web of Documents
Search

Search
Engine

Crawler

The Web is a Data Shredder

Structured Unstructured
Data Data

Thanks Martin Hepp

What would we like?
• Make it easy for computers/software to find
THINGS

Do you SEARCH or do you FIND?

Search for

Football Players who went to the
University of Texas at Austin, played for
the Dallas Cowboys as Cornerback

Why can’t we just FIND it…

On a Semantic Web
• Besides publishing documents on the web
– which computers can’t understand easily
• Let’s publish on the web something that
computers can understand

DATA

The Semantic Web is a
web of data
The current web is a
web of documents

But wait… doesn’t the web
already have data?

Current Data on the Web
• Relational Databases
• APIs
• XML
• CSV
• XLS
• …
• Can’t computers and applications already
consume that data on the web?

Yes! But it is all in different
formats and data models!

This makes it hard to integrate
data

The data in different
data sources aren’t linked

For example, how do I know that the
Juan Sequeda in Facebook is the
same as Juan Sequeda in Twitter

Or if I create a mashup from
different services, I have to learn
different APIs and I get different
formats of data back

Wouldn’t it be great if we had a
standard way of publishing data on
the Web?

We have a standardized way of
publishing documents on the web,
right?
HTML

Then why can’t we have a standard
way of publishing data on the Web?

Good question! And the answer
is YES. There is!
RDF

Resource Description Framework
(RDF)
• Data Model = a way to model data
– i.e. Relational databases use relational data model
• RDF is a graph data model

Key Value vs Graph
• Key Values
– firstName Juan
– lastName  Sequeda
– livesIn  Austin
– knows  Stephane Corlosquet
• But what are these key/values describing?
– ME!

RDF is a Graph
• Let’s group the Key/Values together
– <JuanSequeda> <firstName> “Juan”
– <JuanSequeda> <lastName> “Sequeda”
– <JuanSequeda> <livesIn> “Austin”
– <JuanSequeda> <knows> <StephaneCorlosquet>
– ..
– <StephaneCorlosquet> <firstName> “Stephane”
– <StephaneCorlosquet> <lastName> “Corlosquet”
– <StephaneCorlosquet> <livesIn> “Boston”

Identifier for
the “group” RDF is a Graph Key/Value

• Let’s group the Key/Values together
– <JuanSequeda> <firstName> “Juan”
– <JuanSequeda> <lastName> “Sequeda”
– <JuanSequeda> <livesIn> “Austin”
– <JuanSequeda> <knows> <StephaneCorlosquet>
– ..
– <StephaneCorlosquet> <firstName> “Stephane”
– <StephaneCorlosquet> <lastName> “Corlosquet”
– <StephaneCorlosquet> <livesIn> “Boston”

RDF can be serialized in different ways
• RDF/XML
• RDFa (RDF in HTML)
• N3
• Turtle
• JSON

So does that mean that I have to
publish my data in RDF now?

You don’t have to… but we would
like you to 
Schema.org
Rich Snippets
…

Databases back up documents

THINGS have PROPERTIES:
A Book as a Title, an author, …

Isbn Title Author PublisherID ReleasedData
978-0-596- Programming Toby Segaran 1 July 2009
15381-6 the Semantic
Web
… … … … …

PublisherID PublisherName
This is a THING:
A book title “Programming the 1 O’Reilly Media
Semantic Web” by Toby Segaran, … … …

Lets represent the data in RDF
Isbn Title Author PublisherID ReleasedData

978-0- Programming Toby 1 July 2009
596- the Semantic Segaran
15381- Web
6
Programming the
PublisherID PublisherName title
Semantic Web
1 O’Reilly Media

author
book Toby Segaran

isbn
978-0-596-15381-6
publisher
name
Publisher O’Reilly

Remember that we are on the
web
Everything on the web is identified
by a URI

And now let’s link the data to other
data
Programming the
title
Semantic Web

http://…/i author
Toby Segaran
sbn978

isbn
978-0-596-15381-6
publisher
http://…/p name
ublisher1 O’Reilly

And now consider the data from
Revyu.com
http://…/ hasReview http://…/i
review1 sbn978
description
reviewer

Awesome
Book

http://…/
name
reviewer

Juan
Sequeda

Let’s start to link data
review1 sbn978
Programming the
description title
Semantic Web
hasReviewer owl:sameAs

Awesome author
http://…/i
Book Toby Segaran
sbn978

http://…/
name
reviewer isbn
978-0-596-15381-6
Juan publisher
Sequeda http://…/p name

Juan Sequeda publishes data too

http://juanse livesIn http://dbpedia.org/Austin
queda.com/id name Juan Sequeda

Let’s link more data
review1 sbn978
description
hasReviewer

Awesome
Book

http://…/
name
reviewer

sameAs Juan
Sequeda


And more
review1 sbn978
Programming the
description title
Semantic Web
hasReviewer owl:sameAs

Awesome author
http://…/i
Book Toby Segaran
sbn978

http://…/
name
reviewer isbn
978-0-596-15381-6
owl:sameAs Juan publisher
http://…/p
Sequeda name
ublisher1
O’Reilly

Data on the Web that is in RDF and
is linked to other RDF data is
LINKED DATA

Linked Data Principles
1. Use URIs as names for
things
2. Use HTTP URIs so that
people can look up
(dereference) those
names.
3. When someone looks up
a URI, provide useful
information.
4. Include links to other
URIs so that they can
discover more things.

Linked Data makes the web appear as
ONE
GIANT
HUGE
GLOBAL
DATABASE!

I can query a database with SQL. Is
there a way to query Linked Data
with a query language?

Yes! There is actually a
standardize language for that
SPARQL

FIND all the reviews on the book
“Programming the Semantic Web”
by people who live in Austin

SPARQL

SELECT ?review ?comment
WHERE {
isbn:978 ex:hasReview ?review .
?review ex:description ?comment .
?review ex:hasReviewer ?person .
?person ex:lives dbpedia:Austin .
}

SELECT ?review ?comment
WHERE {
isbn:978 ex:hasReview ?review .
?review ex:description ?comment .
http://…/ hasReview ?review ex:hasReviewer ?person .
http://…/i
review1 ?person ex:lives dbpedia:Austin .
sbn978
}
Programming the
description title
Semantic Web
hasReviewer sameAs

Awesome author
http://…/i
Book Toby Segaran
sbn978

http://…/
name
reviewer isbn
978-0-596-15381-6
sameAs Juan publisher
Sequeda http://…/p name
http://juanse
queda.com livesIn http://dbpedia.org/Austin
name Juan Sequeda

OWL
• Here is where the real semantics shows up
• Web Ontology Language
• Define schema/vocabulary
• Classes, Properties, Inheritance, etc
• Subclasses, Subproperties
• …
• You can get more complicated with rules…

auth: <http://dblp.l3s.de/d2r/page/authors/>
dexa: <http://dblp.l3s.de/d2r/page/publications/conf/dexa/>
dc: <http://purl.org/dc/elements/1.1/>
sw: <http://data.semanticweb.org/person/>
swrc: <http://swrc.ontoware.org/ontology#>
owl: <http://www.w3.org/2002/07/owl#>
rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
rdfs: <http://www.w3.org/2000/01/rdf-schema#>

swrc:Publicatio
n

rdfs:subClassOf

dc:creator
swrc:InProceedings foaf:Person
OWL
rdf:type
owl:sameAs
rdf:type auth:Juan_Sequeda sw:juan-f-sequeda

dc:creator owl:sameAs
dexa:TirmiziSM08 auth:Daniel_P._Miranker sw:daniel-miranker

dc:title owl:sameAs
auth:Syed_Hamid_Tirmizi sw:syed-tirmizi

“Translating SQL
Applications to the
Semantic Web" RDF

RDB and the Semantic Web

TRIGGERS RIF

CONSTRAINTS OWL
TIME

TABLE DEFINITION RDFS

RELATIONAL
RDF
MODEL

74

This looks cool, but let’s be realistic.
What is the incentive to publish
Linked Data?

What was your incentive to
publish an HTML page in 1990?

1) Share data in documents
2) Because you neighbor was doing it
… later on …
3) Marketing, Advertising, …, SEO

So why should we publish
Linked Data in 2011?

1) Share data as data
2) Because you neighbor is doing it
…
3) Marketing, Advertising, SEO ++

Linked Data Publishers
• UK Government
• US Government
• BBC
• Open Calais – Thomson Reuters
• Freebase/Google
• NY Times
• Best Buy
• Sears
• Kmart
• Overstock.com
• CNET
• Dbpedia
• O’Reilly Media
• …

September 2011

Linking Open Data
cloud diagram, by
Richard Cyganiak and
Anja Jentzsch.
http://lod-cloud.net/

YOU GET THE PICTURE
ITS BIG and getting

BIGGER and
BIGGER

What is the Web
• Web of Documents  HTML
• Web of Data  RDF
• Global Unique IDs  HTTP URIs
• Schema/Ontologies  OWL
• Query RDF  SPARQL

Now what can we do with this
data?

Linked Data Browsers
• Not actually separate browsers. Run inside of
HTML browsers
• View the data that is returned after looking up
a URI in tabular form
• User can navigate between data sources by
following RDF Links
• (IMO) No usability

Linked Data Browsers
• http://browse.semanticweb.org/
• Tabulator
• OpenLink Dataexplorer
• Zitgist
• Marbles
• Explorator
• Disco
• LinkSailor

Linked Data (Semantic Web)
Search Engines

Linked Data (Semantic Web)
Search Engines
• Just like conventional search engines (Google, Bing, Yahoo),
crawl RDF documents and follow RDF links.
– Current search engines don’t crawl data, unless it’s RDFa 
• Human focus Search
– Falcons - Keyword
– SWSE – Keyworkd
– VisiNav – Complex Queries
• Machine focus Search
– Sindice – data instances
– Swoogle - ontologies
– Watson - ontologies
– Uberblic – curated integrated data instances

(Semantic) SEO ++
• Markup your HTML with RDFa
• Use standard vocabularies (ontologies)
– Google Vocabulary
– Good Relations
– Dublin Core
• Google and Yahoo will crawl this data and use
it for better rendering

Domain Specific Applications
• Government
– Data.gov
– Data.gov.uk
– http://data-gov.tw.rpi.edu/wiki/Demos
• Music
– Seevl.net
• Dbpedia Mobile
• Life Science
– LinkedLifeData
• Sports
– BBC World Cup

http://dbpedia.neofonie.de/browse/

Find all the locations of all the original
paintings of Modigliani

Select all proteins that are linked to a curated interaction from
the literature and to inflammatory response

http://linkedlifedata.com/

http://tata.csres.utexas.edu:8080/specify/data/taxon51807

http://tata.csres.utexas.edu:8080/specify/data/taxon51807

Links to other Data Sources

Linked Data is Data Integration

SPARQL
Query

Diamond

Ultrawrap
Ultrawrap
Specify Ultrawrap
Morphster
Morphbank

Example 1 (Specify – DBpedia)
• Get full name and guid from taxon with id
http://tata.csres.utexas.edu:8080/specify/data/t
axon51807#thing
• AND fin any subjects it may have “skos:subject”

Result Example 1
• Note that
http://dbpedia.org/resource/Category:Fish_of_
Australia comes from a different data source
(dbpedia.org)

Example 2 (Specify-Morphbank)
• Get full name and guid from taxon with id
axon42947#thing
• AND the rank and kingdom from Morphbank

Result Example 2
• Note that full name and guid come from Specify
axon42947
• AND rank and kingdom come from
Morphbank
http://tata.csres.utexas.edu:8080/morphbank/d
ata/taxa398354

The killer app for A little semantics
Semantic Technology is goes a long way
YOUR life (online) - Jim Hendler
– Tom Gruber
Knowledge is Power
Occupy Your Data - Jim Hendler
- Tim Finin
Linked Data is the
(Semantic) Web done right
The novel part of the - Tim Berners-Lee
Semantic Web is not the
Semantics, but the Web
- Frank van Harmelen RAW DATA NOW
- Tim Berners-Lee

WTF is the Semantic Web and Linked Data

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