introduction to linked data 1/5

Introduction to Linked Data

Juan F. SequedaSemantic Technology Conference

June 2011

What is the Semantic Web?

What is the Semantic Web?

Internet != Web

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 is the problem?

WHAT’S THE WEATHER IN SAN

FRANCISCO TODAY?

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 is a Data Shredder

Structured Data

Unstructured 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…

Guess how I FOUND out?

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 linked data

The current web is a web of linked 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

Data is Siloed

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)

• 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> <has hobby> <Salsa dancing>

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

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 2009

… … … … …

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

Isbn Title Author PublisherID ReleasedData

978-0-596-15381-6

Programming the Semantic Web

Toby Segaran

1 July 2009

PublisherID PublisherName

1 O’Reilly Media

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

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

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

… later on …3) Marketing, Advertising, SEO

So why should we publish Linked Data in 2011?

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

…3) (Semantic) SEO ++

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

May 2007

Oct 2007

Nov 2007

Feb 2008

Mar 2008

Sept 2008

Mar 2009 (1)

Mar 2009 (2)

July 2009

September 2010

June 2011

YOU GET THE PICTURE

ITS BIG and getting

BIGGER and

BIGGER

QUESTIONS?