Introduction to Linked Data

Consuming Linked Data TutorialInternational Semantic Web

Conference 2009

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…

Guess how I FOUND out?

I’ll tell you how I did NOT find it

Current Web = internet + links + docs

So what is the problem?

• The Web has problems– People aren’t interested in documents• They are interested in things

– People can parse documents and extract meaning• Web pages are written in HTML• HTML describes visualization of information• Computers can’t!

What do we need to do?

• We need to help machines to understand the web so machines can help us understand things– They can learn what we are interested in– They can help us better find what we want

How can we do that?

• Besides publishing documents on the web– which computers can’t understand easily

• Let’s publish something that computers can understand

RAW DATA!

But wait… don’t we do that already?

Current Data on the Web

• Relational Databases• APIs• XML• CSV• XLS• …• Can’t computers and applications already

consume that data on the web?

True! 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!

Resource Description Framework (RDF)

• A data model – A way to model data– i.e. Relational databases use relational data model

• RDF is a triple data model• Labeled Graph• Subject, Predicate, Object• <Juan> <was born in> <California>• <California> <is part of> <the USA>• <Juan> <likes> <the Semantic Web>

RDF can be serialized in different ways

• RDF/XML• RDFa (RDF in HTML)• N3• Turtle

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

An example

Document on the Web

Databases back up documents

Isbn Title Author PublisherID ReleasedData

978-0-596-15381-6

Programming the Semantic Web

Toby Segaran 1 July 209

… … … … …

PublisherID PublisherName

1 O’Reilly Media

… …

This is a THING:A book title “Programming the Semantic Web” by Toby Segaran, …

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

Lets represent the data in RDF

book

Programming the Semantic Web

978-0-596-15381-6

Toby Segaran

Publisher O’Reilly

title

name

author

publisher

isbn

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

http://…/isbn978

Programming the Semantic Web

978-0-596-15381-6

Toby Segaran

http://…/publisher1 O’Reilly

title

name

author

publisher

isbn

And now consider the data from Revyu.com

http://…/isbn978

http://…/

review1

Awesome Book

http://…/

reviewer

Juan Sequeda

hasReview

reviewer

description

name

Let’s start to link data

http://…/isbn978

Programming the Semantic Web

978-0-596-15381-6

Toby Segaran

http://…/publisher1 O’Reilly

title

name

author

publisher

isbn

http://…/isbn978

sameAs

http://…/

review1

Awesome Book

http://…/

reviewer

Juan Sequeda

hasReview

hasReviewer

description

name

Juan Sequeda publishes data too

http://juansequeda.

com/id

livesIn

Juan Sequedaname

http://dbpedia.org/Austin

Let’s link more datahttp://…/isbn978

http://…/

review1

Awesome Book

http://…/

reviewer

Juan Sequeda

http://juansequeda.

com/id

hasReview

hasReviewer

description

name

sameAs

livesIn

Juan Sequedaname

http://dbpedia.org/Austin

And more

http://…/isbn978

Programming the Semantic Web

978-0-596-15381-6

Toby Segaran

http://…/publisher1

O’Reilly

title

name

author

publisher

isbn

http://…/isbn978

sameAs

http://…/

review1

Awesome Book

http://…/

reviewer

Juan Sequeda

http://juansequeda.

com/id

hasReview

hasReviewer

description

name

sameAs

livesIn

Juan Sequedaname

http://dbpedia.org/Austin

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

GIANTHUGE

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

http://…/isbn978

Programming the Semantic Web

978-0-596-15381-6

Toby Segaran

http://…/publisher1 O’Reilly

title

name

author

publisher

isbn

http://…/isbn978

sameAs

http://…/

review1

Awesome Book

http://…/

reviewer

Juan Sequeda

http://juansequeda.

com

hasReview

hasReviewer

description

name

sameAs

livesIn

Juan Sequedaname

http://dbpedia.org/Austin

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 documents2) Because you neighbor was doing it

So why should we publish Linked Data in 2009?

1) Share data as data2) Because you neighbor is doing it

And guess who is starting to publish Linked Data now?

Linked Data Publishers 2009

• UK Government• US Government• BBC• Open Calais – Thomson Reuters• Freebase• NY Times• Best Buy• CNET• Dbpedia• Are you?

How can I publish Linked Data?

Publishing Linked Data• Legacy Data in Relational Databases– D2R Server– Virtuoso– Triplify– Ultrawrap

• CMS– Drupal

• Native RDF Stores– Databases for RDF (Triple Stores)

• AllegroGraph, Jena, Sesame, Virtuoso

– Talis Platform (Linked Data in the Cloud)• In HTML with RDFa

Questions?