Linked Data tutorial at Semtech 2012

June 4, 2012

Linked Data
Juan F. Sequeda – Daniel P. Miranker
Capsenta

Semantic Tech & Business Conference 2012
www.capsenta.com 1

Outline
Part 1: Introduction to Linked Data
Part 2: Linked Data Principles
Part 3: Linked Data Architectures
Part 4: Linked Enterprise Data

www.capsenta.com June 4, 2012 2

Part 1:
Introduction to
Linked Data


The Web is a Data Shredder

Structured Unstructured
Data Data
Thanks Martin Hepp

The Web of Documents
Search

Search
Engine

Crawler


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 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
state 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)
Data Model = a way to model data
 i.e. Relational databases use relational data model

RDF is a graph data model


RDF is a Graph
 <JuanSequeda> <firstName> “Juan”
 <JuanSequeda> <lastName> “Sequeda”
 <JuanSequeda> <livesIn> “Austin”
 <JuanSequeda> <knows> <DanielMiranker>
 ..
 <DanielMiranker> <firstName> “Daniel”
 <DanielMiranker> <lastName> “Miranker”
 <DanielMiranker> <livesIn> “Austin”


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


RDFa


RDF/XML


RDF/N-triples


RDF/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

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

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

This is a THING: PublisherID PublisherName
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
title the Semantic
PublisherID PublisherName
Web
1 O’Reilly Media

author Toby
book
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
title the Semantic
Web

http://
…/isbn9 author Toby
78 Segaran

isbn
978-0-596-15381-6
publisher
http://…/
name
publisher O’Reilly
1

And now consider the data from
Revyu.com
http:// hasReview http://
…/revie …/isbn9
w1 78
description
reviewer

Awesome
Book

http:// name
…/revie
wer
Juan
Sequeda


Let’s start to link data
http:// hasReview http://
…/revie …/isbn9
78 Programming
w1 the Semantic
description title
Web
hasReviewer owl:sameAs

Awesome http:// author Toby
Book …/isbn9
Segaran
78
http://…/
reviewer name
isbn
978-0-596-15381-6
Juan publisher
Sequeda http://…/
publisher name
O’Reilly
1

Juan Sequeda publishes data too

http://juans http://dbpedia.org/Au
livesIn stin
equeda.co
www.capsenta.com name Juan Sequeda June 4, 2012 47
m/id

Let’s link more data
http://…/ hasReview http://…/
review1 isbn978
description
hasReviewer

Awesome
Book

http://…/
name
reviewer

sameAs Juan
Sequeda

livesIn stin
equeda.co
m/id

And more
review1 isbn978 Programming
description title the Semantic
Web

Awesome author
http://…/ Toby
Book
isbn978 Segaran

http://…/
reviewer name
isbn 978-0-596-15381-6

owl:sameAs Juan publisher http://…/p
Sequeda ublisher1
name O’Reilly
livesIn stin
equeda.co
m/id

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


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 .
?review ex:hasReviewer ?person .
?person ex:lives dbpedia:Austin .
}
review1 isbn978 Programming
description title the Semantic
Web

Awesome author
http://…/ Toby
Book
isbn978 Segaran

http://…/
reviewer name
isbn 978-0-596-15381-6

owl:sameAs Juan publisher http://…/p
Sequeda ublisher1name O’Reilly
livesIn stin
equeda.co
56
Juan Sequeda
www.capsenta.com name June 4, 2012
m/id

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


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 2012?


1) Share data as data

2) Because you neighbor is doing it

… later on …

3) Marketing, Advertising, …, SEO


Linked Data Publishers
 US and UK Government
 BBC
 NY Times
 Best Buy
 Sears
 Kmart
 Overstock
 … too many more to name


Linked Open Data


http://www.w3.org/DesignIssues/LinkedData.html


May 2007


Oct 2007


Nov 2007


Feb 2008


Mar 2008


Sept 2008


Mar 2009 (1)


Mar 2009 (2)


July 2009


September 2010


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

Part 2:
Linked Data Principles


Linked Data is a set of best practices to
publish and interlink data on the web


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.

1. Use URIs as names for things


1) Use URIs as names for
things

http://dbpedia.org/resource/Austin,_Texas

http://xmlns.com/foaf/0.1/based_near

http://juansequeda.com/foaf.rdf#me http://www.w3.org/People/Berners-Lee/card#i

http://xmlns.com/foaf/0.1/knows

2. Use HTTP URIs so that people
can look up (dereference)
those names.


2) Use HTTP URIs
HTTP client can lookup the URI using HTTP
protocol and retrieve a description



What’s with the redirection (303) ?


http://upload.wikimedia.org/wikipedia/commons/0/06/AustinSkylineLouNeffPoint-2010-03-29-b.JPG


http://dbpedia.org/page/Austin,_Texas

Identifies the abstract concept of
“the city of Austin, Texas”


Accept: text/html Accept: application/rdf+xml

http://dbpedia.org/page/Austin,_Texas http://dbpedia.org/data/Austin,_Texas.xml

Identifies an HTML document that Identifies an RDF document that
describes “the city of Austin, Texas” describes “the city of Austin, Texas”


Minting HTTP URIs
If you own the domain name and run a web
server at that location, mint URIs in this
namespace
I own the domain capsenta.com
I run the webserver http://capsenta.com
I can mint URIs in this namespace
 http://capsenta.com/person/Juan-Sequeda


Cool URIs http://www.w3.org/TR/cooluris/

Don’t misuse a namespace that you don’t own
 http://www.imdb.com/title

Avoid implementation details
 http://capsenta.com/person.php?id=123&format=rdf

Use Natural Keys
 http://capsenta.com/person/123


3. When someone looks up a
URI, provide useful
information.


3) Provide useful information
How do we provide useful information in
document form on the web?  HTML

How do we provide useful information in data
form on the web  RDF


What to publish?
 Literal Triples
<http://dbpedia.org/resource/Austin,_Texas>
<http://xmlns.com/foaf/0.1/name>
“City of Austin”

 Outgoing Link Triples
<http://www.w3.org/2002/07/owl#sameAs>
<http://rdf.freebase.com/ns/m/0vzm>

 Incoming Link Triples
<http://dbpedia.org/resource/Dakota_Johnson>
<http://dbpedia.org/ontology/birthPlace>


What to publish?
Description of the data set
 Semantic Sitemaps
 voiD (Vocabulary of Interlinked Datasets)

Provenance Metadata

Licenses Information


Vocabularies (or Schemas or
Ontologies)
 Create your own using
 RDFS/OWL/ SKOS

 Reuse vocabularies
 Dublin Core: metadata attributes
 Friend of a Friend (FOAF): persons and relationships
 Semantically Interlinked Online Communities (SIOC): describing
users, posts, blogs, etc
 Description of a Project (DOAP)
 Music Ontology
 Programmes Ontology: TV and radio programs
 Good Relations: describing products and services
 Review Vocabulary
 Basic Geo (WGS84) Vocabulary


4. Include links to other URIs so
that they can discover more
things.


4) Include links to other things
Set external RDF links into other data sources on
the Web
 Subject of the triple is in the namespace of one data
set
 Object of the triple is a URI in the namespace of
another data set

Connect siloed data islands
Enable discovery


4) Include links to other things
 Relationship Link Triples
<http://juansequeda.com/foaf.rdf#me>
<http://xmlns.com/foaf/0.1/based_near>

 Identity Link Triples
<http://www.w3.org/2002/07/owl#sameAs>
<http://rdf.freebase.com/ns/m/0vzm>

 Vocabulary Link Triples
<http://capsenta.com/vocab/name>
<http://www.w3.org/2002/07/owl#equivalentProperty>
<http://xmlns.com/foaf/0.1/name>


Which predicate for linking to
choose?
Depends on your domain
Is it widely used?
 owl:sameAs
 foaf:knows
 foaf:based_near
…

If you create your own, relate it to a widely
used predicate


Part 3:
Linked Data
Architectures


Static RDF Files
Small amount of data (personal FOAF file)
Use RDF/XML serialization
Save as .rdf file and upload it to your server
 http://www.capsenta.com/company.rdf
 http://www.capsenta.com/company.rdf#this
Configure MIME types
 AddType application/rdf+xml .rdf

Make RDF discoverable from HTMl
 <link rel="alternate" type="application/rdf+xml" href="company.rdf">


RDF in HTML (RDFa)
Another syntax for RDF

Useful if you have template HTML pages

Drupal 7 will do this out of the box


Triplestores (aka RDF db, …)
Commercial
 Oracle, IBM, OntoText (OWLIM), Franz (Allegrograph),
Openlink (Virtuoso), C&P (Stardog), Ontoprise
(OntoBroker), Meronymy

Open Source
 Jena, Sesame, Mulgara, 4Store (Garlik), BigData
(Systap)


RDB2RDF
 Upcoming W3C RDB2RDF Standards
 R2RML: mapping language
 Direct Mapping: default automatic mapping

 Two Approaches
 Dynamic (SPARQL to SQL)
 ETL (Dump RDB to RDF)

 Ultrawrap
 Supports W3C standard and more
 SPARQL as fast as SQL


Unstructured to RDF

Triplestore

Entity Extractor

Unstructured


Semi-structured to RDF

Triplestore

XML2RDF,
XLS2RDF,
CVS2RDF

Semi-structured


RDB to RDF

CMS with RDFa, RDB2RDF
Semantic Wiki (SPARQL to SQL) Triplestore

RDB2RDF
ETL

Relational
Database


Creating Linked Data
Linked Data

CMS with Data
Linked Data RDB2RDF Custom Linked
Web Server RDFa, Semantic
Interface (i.e. Ultrawrap) Data Wrapper Publication
Wiki

RDB2RDF
Data source
Data
Triplestore RDB
with API Storage

XML2RDF, Data
Entity Extractor
XLS2RDF, CVS2RDF
Preparation

Unstructured Semi-structured Structured Type of Data

Thanks Heath and Bizer

Consuming Linked Data
Application

Schema Mapping Record Linkage Provenance Tracking

Data Access

Linked Data



Schema Matching
 Renaming
 <ex:name>  <foaf:name>
 owl:equivalentClass and owl:equivalentProperty
 rdfs:subClass or rdfs:subProperty

 Structural Transformation
 <ex:Juan> <ex:lives> “Austin”
 <ex:Juan><foaf:based_near><db:Austin> .
<db:Austin><rdfs:label> “Austin”.

 SPARQL Construct, RIF, R2R


Record Linkage
Different URIs that identify the same thing
Create owl:sameAs links between them

Manually lookup: Sindice

(Semi) Automatically: SILK


Provenance
Keep track where the data is coming from
 Quality
 Trust

Named Graphs
SPARQL Graph


Centralized
Application

SPARQL

Triplestore



Centralized
Advantage
 Include the datasets that you need
 Complex queries and high performance
 Reasoning

Drawbacks
 Depends on RDF dumps or crawling
 Effort to setup the centralized triplestore
 Queried data may be out of date


Federated
Application

SPARQL

Federator

SPARQL SPARQL
SPARQL SPARQL

RDB2RDF RDB2RDF
Triplestore Triplestore
Relational Relational
Database Database


Federated
Advantage
 Include the datasets that you need
 Queried data is up to date

Drawbacks
 Requires existence of a SPARQL endpoint
 Effort to setup federator


Linked Traversal
Application

SPARQL

Linked Traversal Query Engine

Linked Data

RDB2RDF
Triplestore
Relational
Database

Linked Traversal
Advantage
 No need to know the data sources in advance
 Does not depend on the existence of SPARQL
endpoints or RDF dumps
 Queried data is up to date
Drawbacks
 Query execution time is slow
 Unsuitable for some queries
 Results may be incomplete
 Still in research


Applications
Linked Data Browsers
 http://browse.semanticweb.org/
Linked Data (Semantic Web) Search Engines
 Falcons, SWSE, VisiNav, Sindice, Sigma, Swoogle, Wats
on
Search Engines
 Google, Bing, Yahoo!
Faceted Browsers
 http://dbpedia.neofonie.de/browse/


Domain Specific Applications
BBC World Cup

Seevl.net

Linked Life Data

Government apps

Part 2:
Linked Enterprise Data


Use
internally
Consume
Linked (Open) Data

Publish
Linked (Open) Data


Linked Data can be used as an architectural
style for integrating data in the Enterprise

1. Standard Data Access Mechanism: HTTP
2. Standard Address & Identifier Scheme: URI
3. Standard Data Model: RDF


Information creation  information sharing
Produce and consume data specific to your
needs but also produce it in a way that it can
be connected to other data in the enterprise
Distributed but connected!
Data that you create, may benefit others!
Share it!


Benefits of RDF/Linked Data
RDF (graphs) is a least common denominator
 Text, CVS, XML, XLS, RDB to RDF
 Imagine modeling a social network in XML

Dynamic and Flexible
 Adding a column to a table in my RDBMS takes 6
months to authorize!
 With RDF, simply add the triple!
 Incremental


Benefits of RDF/Linked Data
Power of the URI and Links
 Universal Identifier
 Create a “foreign key” to a table that I have no
control of

Scalability in months, not only seconds
 “More can be done with less and faster”
 “Cooperation without coordination”


What’s next?
W3C Linked Data Platform Working Group
 http://www.w3.org/2012/ldp/charter

Linked Data Basic Profile 1.0
 http://www.w3.org/Submission/ldbp/


Summary


Linked Data Checklist
Does your data link to other data sets?
Do you provide provenance metadata?
Do you provide licensing metadata?
Do you reuse common vocabularies?
Do you map proprietary vocabulary terms to
common vocabularies?
Do you provide other access methods?
Thanks Heath & Bizer
www.capsenta.com June 4, 2012

Acknowledgements
 RiBS Lab – UT Austin
 Olaf Hartig – Humboldt University Berlin
 Patrick Sinclair – BBC
 Jamie Taylor – Google

 Tom Heath & Chris Bizer. Linked Data: Evolving the
Web into a Global Data Space
 David Wood (Ed.). Linking Enterprise Data


Thanks!
Juan F. Sequeda Daniel P. Miranker

juan@capsenta.com miranker@capsenta.com

@juansequeda

www.capsenta.com


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