Intro to Linked Data: Context

An
Introduction
to
Linked Data

Part 1 of 5 David Hyland-Wood
Linked Data Context University of Mary Washington

Monday, May 16, 2011

Agenda

• Setting the scene

• What is Linked Data?

• RDF - A data format for the Web

• Data modeling without context

• URIs - Naming Things on the Web


Agenda
• Turtle - Human-readable RDF

• RDF/XML - RDF for XML pipelines

• Other RDF formats: RDFa, N3

• RDF Schema - Describing structure


Agenda

• Converting existing data into RDF

• Linked Open Data on the Web

• SPARQL - A query language for RDF

• Linked Data publishing options

• Building Linked Data applications


Reading

http://linkeddatabook.com/editions/1.0/

http://3roundstones.com/linking-enterprise-data/


Final Project
• Collect/convert/publish data about
Fredericksburg

• UMW, restaurants, Liberty Town,
parks/rec, music/bands, etc, etc.

• Whatever you want.

• Together, we will build one or more
applications using that data.


Grades

• Grades will be based on class
participation and completion of the
ﬁnal project.


A Process

Identify Model Name Describe Convert Publish


A Process

Identify Model Name Describe Convert Publish

Maintain


Setting
the
Scene

shared innovation™

A HISTORY OF SILOS

$ cat foo.txt
| grep blah |
sort

1970s 1980s 1990s
A neat little package Client-Server The Early Web


shared innovation™

Universal Client Ubiquitous,
reusable applications

URL Curation

Universal Connection Logic and interlinking

Web
of Data
Universal Database


Access per 100 population worldwide
80

70 Mobile cellular subscriptions
60 Fixed telephone lines
Internet users
50

40

30

20

10

0
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

Data Inﬂation
Megabyte (MB) = 220
Gigabyte (GB) = 230
Terabyte (TB) = 240 1,000GB
Petabyte (PB) = 250 1,000TB
Exabyte (EB) = 260 or 1,000PB
Zettabyte (ZB) = 270 or 1,000EB
Yottabyte (YB) = 280 or1,000ZB


March of the Machines

“Information created by machines and used by
other machines will probably grow faster than
anything else...

Only 5% of the information that is created is
structured but this is changing as content
on the Web is increasing tagged.”

- Roger Bohn of University of California, San Diego
Study on American Households


The painter... does not ﬁt the paints to the world.
He ﬁts himself to the paint.
-- Paul Klee


Acceptable ROI for IT
4% 17%
13%

16%

6 months
49% 12 months
18 months
24 months
More than 24 months


What is
Linked
Data?

The Web of Documents
• A global network of linked documents
• A place where anyone can say
anything about anything
• A vast collection of human-readable
knowledge (and opinion)
• Documents are linked, but links are not
qualiﬁed


The Web of Data
• A global network of linked statements
• A place where anyone can say
anything about anything
• A vast collection of machine-readable
knowledge (and opinion)
• Statements are linked, and links are
qualiﬁed


The Web of Data
• Modeled for re-use using simple
statements
• Named using HTTP URIs for things and
for documents
• Described using simple schema which
can be remixed and extended
• Data published on the web in RDF


The Web of Data
• Governments
http://data.gov/, http://data.gov.uk/ and others

• The BBC
http://www.bbc.co.uk/programmes/developers

• The New York Times
http://data.nytimes.com/

• The Library of Congress
http://id.loc.gov/

• Facebook
http://developers.facebook.com/docs/opengraph
http://opengraphprotocol.org/


RDF:
A data format for
the Web

RDF is ...
• Resource Description Framework
http://www.w3.org/RDF/

• A simple, powerful, data model
• Used to deﬁne relationships between
things
• Designed to work with the architecture of
the web
• The data model for the Web of Data


Allow anyone
to say anything
about anything


http://nssdc.gsfc.nasa.gov/
nmc/spacecraftDisplay.do?
id=1969-059A


id=1969-059A

NASA - NSSDC - Spacecraft - Details
title


id=1969-059A

title

23 November 2009
published


id=1969-059A

title

23 November 2009
published

size
15702


Apollo 11 Command and
Service Module
id=1969-059A

title

23 November 2009
published

size
15702


http://nssdc.gsfc.nasa.gov/ about Apollo 11 Command and
Service Module
id=1969-059A

title

23 November 2009
published

size
15702


Service Module
id=1969-059A

title

23 November 2009
published

size
15702

a
Web Page


Service Module
id=1969-059A

title

23 November 2009
published

size
15702

a a
Web Page Spacecraft


Service Module
id=1969-059A

name
NASA - NSSDC - Spacecraft - Details Apollo 11 Command and Service Module
title

23 November 2009
published

size
15702

a a
Web Page Spacecraft


Service Module
id=1969-059A

name
title

launched
23 November 2009 16 July 1969
published

size
15702

a a
Web Page Spacecraft


Service Module
id=1969-059A

name
title

launched
23 November 2009 16 July 1969
published

size mass
15702 28801.0

a a
Web Page Spacecraft


Spacecraft Name Mass Launched Launch Site

1969-018A Apollo 9 26801.0 1969-03-03 1

1969-030A Mariner 7 411.8 1969-03-27 1

1969-043A Apollo 10 28834.0 1969-05-18 1

1969-059A Apollo 11 Command and Service Module (CSM) 28801.0 1969-07-16 1

1969-059C Apollo 11 Lunar Module / EASEP 15065.0 1969-07-16 1


1970-029C Apollo 13 Lunar Module/ALSEP 15196.0 1970-04-11 1



Spacecraft Name Mass Launched Launch Site

1969-018A Apollo 9 26801.0 1969-03-03 1

1969-030A Mariner 7 411.8 1969-03-27 1

1969-043A Apollo 10 28834.0 1969-05-18 1
ID Name
1 Cape Canaveral, United States
1969-059C Apollo 11 Lunar Module / EASEP 15065.0 1969-07-16 1
2 Tyuratam (Baikonur Cosmodrome), U.S.S.R
3 Xichang Space Launch Center
1970-029C Apollo 13 Lunar Module/ALSEP 15196.0 1970-04-11 1



Apollo 11 Command and
Service Module

name
Apollo 11 Command and Service Module

launched
16 July 1969

mass
28801.0

a
Spacecraft


Apollo 11 Command and launchsite
Cape Canaveral
Service Module

name name
Apollo 11 Command and Service Module Cape Canaveral, United States

launched
16 July 1969

mass
28801.0

a
Spacecraft


Resource

Cape Canaveral
Service Module

name name

launched
16 July 1969

mass
28801.0

a
Spacecraft


Resource

Cape Canaveral
Service Module

name name

launched
16 July 1969

Literal

mass
28801.0

a
Spacecraft


Resource

Cape Canaveral
Service Module

name name

launched
16 July 1969

Literal
Predicate
mass
28801.0

a
Spacecraft


Resources...
• Represent things on the web, like web
pages — Information Resources
• Represent things not on the web, like
people and places — Non-Information
Resources
• Can represent anything at all
• Named using URIs (usually)
• May not have a name — Blank Nodes


Literal Values...
• Are values to work with and show
users
• Can be just a string of text — Plain
Literals
• Can have a language assigned to the
them using ISO codes
• Can have a speciﬁc datatype assigned
to them — Typed Literals


Predicates are...
• Relationships between Resources
• Named using URIs
• Described in Schema
(or vocabularies, or ontologies)


Apollo 11 Command and launchsite name Cape Canaveral,
Cape Canaveral
Service Module United States

Statement or Triple


Subject Predicate Object

Cape Canaveral

Statement or Triple


Statement or Triple


Cape Canaveral

Statement or Triple


Statement or Triple


Cape Canaveral


Statement or Triple


http://...
Apollo 11 Command and launchsite http://...
Cape Canaveral
Service Module
/1969-059A /cape+cana...

name name

launched
16 July 1969

mass
28801.0

a http://...
Spacecraft
/Spacecraft


http://...
Apollo 11 Command and launchsite http://...
Cape Canaveral
Service Module
/1969-059A /cape+cana...

name name

launched
16 July 1969

mass
28801.0

a http://...
Spacecraft latitude
/Spacecraft N 28° 27' 31''

longitude
W 80° 31' 59''


Simple Rules for Merging
• URIs name the resources we are
describing
• Two people using the same URI are
describing the same thing
• The same URI in two datasets
becomes one URI with all of the
properties from both datasets
• RDF data can use URIs from many
different websites


Simple Rules for Merging
• Graphs from several different sources
can be merged
• Resources with the same URI are
considered identical
• No limitations on which graphs can be
merged


Any RDF can be
merged with any
other RDF


RDF...
• is a Graph data model
XML is a tree data model
RDBMS is a table data model

• can be easily distributed
• is easily mergeable
• can say anything about anything
• is not new
the spec is from 1999
the idea, EAV, stems back to the late 1960s


Thanks to

• Rob Styles, Talis Group Ltd for his CC-BY
licensed “Two Day Introduction to the Web of
Data” slides and spacecraft example data.


This work is Copyright © 2010 David Hyland-Wood
Based partially on CC-BY licensed content Copyright © 2010 Talis Systems Limited by Rob Styles.
It is licensed under the Creative Commons Attribution 3.0 Unported License.
Full details at: http://creativecommons.org/licenses/by/3.0/

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