Digital Enterprise Research Institute www.deri.ie
Hello Open World!
The Web of Data for the Pragmatic Developer
Alexandre Passant & Michael Hausenblas
WWW09, Madrid, Spain 2009-04-20
© Copyright 2008 Digital Enterprise Research Institute. All rights reserved.

Outline
Digital Enterprise Research Institute www.deri.ie
Content

Motivation

What is the Web of Data?

Creating Structured Data

Discovery, Accessing & Querying

Mash-ups & Advanced Topics

2

Speakers introduction
Digital Enterprise Research Institute www.deri.ie
Alexandre Passant

Postdoctoral researcher, DERI Galway

Social Software and Semantic Web

http://apassant.net

Michael Hausenblas

Postdoctoral researcher, DERI Galway

Large-scale Data/Linked Data and Multimedia

http://sw-app.org

3

What is this tutorial about
Digital Enterprise Research Institute www.deri.ie
What you will learn

Web of Data principles

Finding and creating structured data

Ontologies and lightweight inference

Storing and querying RDF data with SPARQL

User interfaces and mash-ups for the Web of Data

What you will not

Ontology mapping and alignment

Advanced rules languages

Complex SPARQL querying

4

What you should be able to do after this
tutorial
Digital Enterprise Research Institute www.deri.ie
Explain the Web of Data to your CTO / Students /

Advisor / Grandmother
Spread the values of the Web of Data

Publish Linked Data

And participate in the Linking Open Data community effort

to expand the network effort of the Web of Data
Build applications for the Web of Data

Using open-source and xAMP technologies

Creating, consuming and mashing-up RDF data

5

Outline
Digital Enterprise Research Institute www.deri.ie
Content

Motivation

What is the Web of Data?

Creating Structured Data

Discovery, Accessing & Querying

Mash-ups & Advanced Topics

6

Motivation
Digital Enterprise Research Institute www.deri.ie
2007
2008
7

Motivation
Digital Enterprise Research Institute www.deri.ie
2008
2009
8

Motivation
Digital Enterprise Research Institute www.deri.ie
More and more data is available on the Web

Structured data, in RDF, microformats, etc.

Up to now people would develop against

proprietary APIs (such as from Flickr, Google, etc.)
Loss of time for developers

The Web of Data …

Provides a uniform data model (RDF)

Provides a uniform API for accessing data (RDF/SPARQL)

Provide common semantics for this data (RDFS/OWL)

Is a scalable platform for data integration and mash-up

Enables serendipitous usage of data

9

Outline
Digital Enterprise Research Institute www.deri.ie
Content

Motivation

What is the Web of Data?

Creating Structured Data

Discovery, Accessing & Querying

Mash-ups & Advanced Topics

10

What is the Web of Data?
Digital Enterprise Research Institute www.deri.ie
In contrast to the full-fledged Semantic Web vision,
the Web of Data is about publishing structured
data in RDF using URIs rather than focusing on the
ontological level or inference.
 This simplification (just as the Web simplified the
established academic approaches of Hypertext
systems) lowers the entry barrier for data providers
and consumers, hence fosters a wide-spread
adoption and real-world impact.
11

What is the Web of Data?
Digital Enterprise Research Institute www.deri.ie
12

What is the Web of Data?
Digital Enterprise Research Institute www.deri.ie
Linked data principles, by Tim Berners-Lee, ca.

2006
Use URIs to identify things (anything, not just documents)

Use HTTP URIs – globally unique names, distributed

ownership – allows people to look up things
Provide useful information in RDF – when someone looks

up a URI
Include RDF links to other URIs – to enable discovery of

related information
13

What is the Web of Data?
Digital Enterprise Research Institute www.deri.ie
Ongoing work

Description/discovery

– semantic sitemaps, see
http://sw.deri.org/2007/07/sitemapextension/
– voiD, see http://semanticweb.org/wiki/VoiD
Trust (SPOT09 at ESWC09 for example)

Multimedia/Fragments, see

http://www.interlinkingmultimedia.info/
Foundational issues in TAG/AWWSW

Transforming the read-only Web of Data into a read/write

Web of Data, see for example
http://esw.w3.org/topic/PushBackDataToLegacySources
14

What is the Web of Data? - URIs
Digital Enterprise Research Institute www.deri.ie
Architecture of the World Wide Web, vol. 1

http://www.w3.org/TR/webarch/

“To benefit from and increase the value of the World Wide

Web, agents should provide URIs as identifiers for
resources”
URIs are used to identifying anything that can be

represented on the Web: pages but also people,
cities, interests …
But people are not documents !

15

What is the Web of Data? - URIs
Digital Enterprise Research Institute www.deri.ie
A Uniform Resource Identifier (URI) is a compact

sequence of characters that identifies an abstract
or physical resource as of RFC3986
Syntax

URI = scheme \":\" hier-part [ \"?\" query ] [ \"#\" fragment ]
Example

foo://example.com:8042/over/there?name=ferret#nose
\\_/ \\_________________/\\_________/ \\__________/ \\__/
| | | | |
scheme authority path query fragment
16

What is the Web of Data? - URIs
Digital Enterprise Research Institute www.deri.ie
Don’t confuse scheme with protocol

Scheme: defines URI layout and (certain) semantics; go and

register with IANA using RFC4395
Protocol: defines communication means between

endpoints (such as HTTP, FTP, etc.)
URI resolution (as of RFC3986)

STEP OUTPUT BUFFER INPUT BUFFER
1: /a/b/c/./../../g
2E: /a /b/c/./../../g
2E: /a/b /c/./../../g
2E: /a/b/c /./../../g
2B: /a/b/c /../../g
2C: /a/b /../g
2C: /a /g
2E: /a/g
17

What is the Web of Data? - URIs
Digital Enterprise Research Institute www.deri.ie
URIrefs, URI references

An RDF URI reference is a Unicode string does not contain
any control characters (#x00 - #x1F, #x7F-#x9F) and would
produce a valid URI character sequence representing an
absolute URI when subjected to an UTF-8 encoding along
with %-escaping non-US-ASCII octets.
QNames, Qualified Names (see XML Namespaces)

XML’s way to allow namespaced elements/attributes as of
QName = Prefix ‘:‘ LocalPart
CURIEs, Compact URIs

Generic, abbreviated syntax for expressing URIs, currently

in SPARQL, RDFa, and XHTML2 deployed
18

What is the Web of Data? - HTTP
Digital Enterprise Research Institute www.deri.ie
The Hypertext Transfer Protocol (HTTP) is an

application-level protocol for distributed,
collaborative, hypermedia information systems. It is
a generic, stateless, protocol which can be used
for many tasks beyond its use for hypertext, such
as name servers and distributed object
management systems, through extension of its
request methods, error codes and headers. A
feature of HTTP is the typing and negotiation of
data representation, allowing systems to be built
independently of the data being transferred.
[RFC2616]
19

What is the Web of Data? - HTTP
Digital Enterprise Research Institute www.deri.ie
HTTP messages consist of requests from client to

server and responses from server to client
Set of methods is predefined (such as GET, POST,

etc.), but can be expanded
Set of status codes is defined

Informational 1xx, provisional response, (100 Continue)

Successful 2xx, request successfully received, understood, and

accepted (201 Created)
Redirection 3xx, further action needs to be taken by user agent

to fulfill the request (301 Moved Permanently)
Client Error 4xx, client erred (405 Method Not Allowed)

Server Error 5xx, server encountered an unexpected condition

(501 Not Implemented)
20

What is the Web of Data? - HTTP
Digital Enterprise Research Institute www.deri.ie
GET /html/rfc2616 HTTP/1.1
REQUEST
Host: tools.ietf.org
User-Agent: Mozilla/5.0
Accept: text/html,application/xhtml
+xml,application/xml;q=0.9,*/*;q=0.8
RESPONSE
HTTP/1.x 200 OK
Date: Thu, 05 Mar 2009 08:17:33 GMT
Server: Apache/2.2.11
Content-Location: rfc2616.html
Last-Modified: Tue, 20 Jan 2009 09:16:04 GMT
Content-Type: text/html; charset=UTF-8
21

What is the Web of Data? - HTTP
Digital Enterprise Research Institute www.deri.ie
Content Negotiation (CN, conneg) is the process of

selecting the best representation for a given
response when there are multiple representations
available
Three types of CN: server-driven, agent-driven CN,

transparent CN
Example

curl -I -H \"Accept: application/rdf+xml\" http://dbpedia.org/resource/Galway
HTTP/1.1 303 See Other
Content-Type: application/rdf+xml
Location: http://dbpedia.org/data/Galway.rdf
22

What is the Web of Data? - HTTP
Digital Enterprise Research Institute www.deri.ie
Caching (see Cache–Control header field) is

essential for scalability
HTTPbis, IETF WG chaired by Mark Nottingham,

mainly about: patches, clarifications, deprecate
non-used features, documentation of security
properties
23

What is the Web of Data? - HTTP
Digital Enterprise Research Institute www.deri.ie
Representational State Transfer

resource the intended conceptual target of a hypertext
reference
resource identifier URL, URN
representation HTML document, JPEG image
representation media type, last-modified time
metadata
resource source link, alternates, vary
metadata
control data if-modified-since, cache-control
24

What is the Web of Data? - RDF
Digital Enterprise Research Institute www.deri.ie
As of RDF abstract syntax, a data model: a directed,

labeled graph based on URIs
RDF is not XML !

RDF/XML is only one of the multiple way to serialize RDF

data (N3, RDFa …)
Triple: (subject predicate object)

subject … URIref or bNode

predicate … URIref

object … URIref or bNode or literal

<http://sw-app.org/#i> <http://xmlns.com/foaf/0.1/knows>
<http://apassant.net/alex>.
25

What is the Web of Data? - RDF
Digital Enterprise Research Institute www.deri.ie
26

What is the Web of Data? - Ontologies
Digital Enterprise Research Institute www.deri.ie
Ontologies provide common semantics for the Web

of Data
“An ontology is a specification of a conceptualization.”

Main languages are RDFS and OWL

This tutorial will mainly focus on RDFS

OWL allows advanced axioms (contraints, unions …)

Classes and properties

:Person a rdfs:Class

:father a rdfs:Property

:father rdfs:domain :Person

:father rdfs:range :Person

27 of XYZ

What is the Web of Data? - Ontologies
Digital Enterprise Research Institute www.deri.ie
Hierarchies in ontologies

Are needed to define narrower / broader concepts

:LivingThing > :Person

Can be applied to both classes and properties

:Person rdfs:subClassOf :LivingThing

:father rdfs:subPropertyOf :familyRelation

Inference engines can take advantage of it to create

new facts
Can be used when querying information

Retrieve all :LivingThing instances with a :familyRelation

– Will get :Person and :father
28 of XYZ

What is the Web of Data? – Open World
Digital Enterprise Research Institute www.deri.ie
The Open World Assumption

Might be complex to understand when coming from a

RDBMS or OOP background
If a fact is not there, it does not means it is false

Bob’s father is Paul. Is Jim Paul’s father ?

– Cannot be answered unless there are some cardinality
constraints in the ontology (in OWL), e.g. a Person has only 1
father.
Is John a speaker in this tutorial ?

– Cannot be answered
Bob’s daughters are Alice and June. Has Bob 3 daughters ?

– Cannot be answered
29 of XYZ

What is the Web of Data? – Open World
Digital Enterprise Research Institute www.deri.ie
Domain and range of properties are descriptive, not

prescriptive
:father rdfs:domain :Person

Does not mean that only pre-defined instances of :Person

can be linked to other via a :father relationship, but that
each instance linked to another via :father becomes
instantaneously a foaf:Person
– Based on RDF semantics (Rule rdfs2)
– http://www.w3.org/TR/rdf-mt/
Once again, constraints are needed to check integrity of a

model and a knowledge base
– E.g. to check that inferred statements are not contradictory
with OWL axioms such as owl:disjoinwWith
30 of XYZ

What is the Web of Data? - Overview
Digital Enterprise Research Institute www.deri.ie
Web's Standard Retrieval Algorithm as of [SDD]:
1. parse URI and find HTTP protocol
2. look up DNS name to determine the
associated IP address
3. open a TCP stream to port 80 at the IP
address determined above
4. format an HTTP GET request for resource
and sends that to the server
5. read response from the server
6. from the status code (200) determine that a
representation of the resource is available
7. inspect the returned Content-Type
8. pass the entity-body to its HTML rendering
engine
31

Digital Enterprise Research Institute www.deri.ie
32

What is the Web of Data? - Overview
Digital Enterprise Research Institute www.deri.ie
33

What is the Web of Data? - Overview
Digital Enterprise Research Institute www.deri.ie
34

Applications for the Web of Data
Digital Enterprise Research Institute www.deri.ie
Towards a reference architecture for Semantic Web applications.
Heitmann et al. (WebSci09 – http://journal.webscience.org/199/)
35 of XYZ

Linking Open Data Project
Digital Enterprise Research Institute www.deri.ie
Community project with W3C support started in

early 2007 [LOD]
Idea: take existing (open) data sets and make

them available on the Web in RDF
Interlink them with other data sets

Kudos to Tom Heath and Richard Cyganiak;
the material in this section is heavily based on
their work.
36

Linking Open Data Project
Digital Enterprise Research Institute www.deri.ie
May 2007
37

Linking Open Data Project
Digital Enterprise Research Institute www.deri.ie
Feb 2009
38

Linking Open Data Project
Digital Enterprise Research Institute www.deri.ie
DBpedia
39

Linking Open Data Project
Digital Enterprise Research Institute www.deri.ie
Geonames
40

Tools and Applications
Digital Enterprise Research Institute www.deri.ie
Linking Open Data homepage [LOD] has

Browsing with Tabulator, VisiNav, DBpedia Mobile, iLOD,

etc.
Searching with Sindice, SWSE, Falcons, etc.

Mashups, e.g. Revyu, BBC Music, DERI Pipes

See further

http://esw.w3.org/topic/SweoIG/TaskForces/
CommunityProjects/LinkingOpenData/Applications
41

Tools and Applications
Digital Enterprise Research Institute www.deri.ie
DBpedia Mobile
42

Tools and Applications
Digital Enterprise Research Institute www.deri.ie
BBC music beta
43

Outline
Digital Enterprise Research Institute www.deri.ie
Content

Motivation

What is the Web of Data?

Creating Structured Data

Discovery, Accessing & Querying

Mash-ups & Advanced Topics

44 of XYZ

Creating Structured Data
Digital Enterprise Research Institute www.deri.ie
Overview of different methods:

Create RDF/XML manually (using your favourite text-editor

or Web-based interfaces)
Create XHTML+RDFa documents and use GRDDL

transformation
Use exporters / wrappers for existing service

Use applications that natively expose RDF data

Provide mappings from RDBMS to RDF data

Hands-on !

We will go through several of them to create interlinked

RDF data from various sources of structured data
45 of XYZ

Getting a FOAF profile
Digital Enterprise Research Institute www.deri.ie
Or how to give yourself a URI

FOAF is the main vocabulary to describe people,

their interests, their social networks
http://foaf-project.org

http://xmlns.com/foaf/0.1

Create your FOAF file

http://www.ldodds.com/foaf/foaf-a-matic (requires

hosting - provided during the tutorial)
http://foafbuilder.qdos.com/builder/ (requires OpenID)

46 of XYZ

Extend your FOAF profile
Digital Enterprise Research Institute www.deri.ie
The foaf:knows property aims to represent social

connections between people
:alex foaf:knows :michael

Going further with the relationship vocabulary

http://vocab.org/relationship/: colleagueOf, hasMet …

Add some people from the workshop, validate, and

upload to the workshop repository
http://www.w3.org/RDF/Validator/

http://helloopenworld.net/www2009/data

You finally got a URI !

– http://helloopenworld.net/www2009/data/apassant.rdf#me
47 of XYZ

Defining personal interests
Digital Enterprise Research Institute www.deri.ie
Instead of modeling interests as plain-text strings,

use URIs to describe them !
Allows interlinking of various resources for advanced

query purposes: “find all people that like movies directed
by Tarantino”
And link them to you using foaf:topic_interest

:me foaf:topic_interest :movie

But … where to get these URIs ?

The Linking Open Data cloud !

– Provide URIs for million of concepts, esp. thanks to DBpedia
Sindice can be used to find URIs for a given concept

– http://sindice.com
48 of XYZ

Defining personal interests
Digital Enterprise Research Institute www.deri.ie
49 of XYZ

Defining personal interests
Digital Enterprise Research Institute www.deri.ie
50 of XYZ

Extending a vocabulary
Digital Enterprise Research Institute www.deri.ie
The semantics of foaf:topic_interest can be too

weak
How to explicitly create a relationship between someone

and his favorite(s) movie(s) and not any kind of interest ?
Extending FOAF by creating your own property

And declare it as a subproperty of foaf:topic_interest

Vocabularies hosting with OpenVocab

Collaborative ontology editing

http://open.vocab.org

http://open.vocab.org/forms/newprop

51 of XYZ

RDFa and GRDDL
Digital Enterprise Research Institute www.deri.ie
GRDDL is a mechanism to transform any kind of

XML to RDF
XHTML+RDFa is an XML application, hence GRDDL

can be used to glean the RDF graph from it
INRIA/Fabien Gandon provided such an

transformation based on XSLT, now available at
http://www.w3.org/2008/07/rdfa-xslt
52 of XYZ

RDFa and GRDDL
Digital Enterprise Research Institute www.deri.ie
The GRDDL Primer at

http://www.w3.org/TR/grddl-primer/#scheduling
shows the overall processing of XHTML+RDFa:
53 of XYZ

RDFa and GRDDL
Digital Enterprise Research Institute www.deri.ie
http://sdow2009.semanticweb.org

54 of XYZ

RDFa and GRDDL
Digital Enterprise Research Institute www.deri.ie
http://sdow2009.semanticweb.org

Browse source to check RDFa annotations

55 of XYZ

RDFa and GRDDL
Digital Enterprise Research Institute www.deri.ie
http://sdow2009.semanticweb.org

Header contains prefixes and links to the GRDDL

transformation
56 of XYZ

RDFa and GRDDL
Digital Enterprise Research Institute www.deri.ie
http://sdow2009.semanticweb.org

Webpage can be translated to native RDF/XML using an

RDFa distiller - http://www.w3.org/2007/08/pyRdfa/
57 of XYZ

Wrappers for existing sources
Digital Enterprise Research Institute www.deri.ie
Creating and maintaining a FOAF file by hand can

be a time-consuming task
How can we automatically get RDF data from existing

sources ?
What about Web 2.0 services in which we already

give lots of personal information ?
Most of them provide APIs to get structured information

(JSON, XML …) about the user profiles, content, etc.
API to RDF wrappers can easily be implemented

58 of XYZ

Wrappers for Web 2.0 services
Digital Enterprise Research Institute www.deri.ie
Facebook wrapper

Generates a FOAF file from your Facebook profile

http://www.dcs.shef.ac.uk/~mrowe/foafgenerator.html

Flickr wrapper

Generates FOAF + SIOC + links to geographical information

(using geonames.org)
http://apassant.net/home/2007/12/flickrdf

OpenLink URIBurner

Translates many structured sources into RDF

E.g. Twitter:

– http://linkeddata.uriburner.com/about/rdf/http://
twitter.com/terraces
59 of XYZ

Interlinking identities
Digital Enterprise Research Institute www.deri.ie
The previous exporters create different URIs

A need to unify your online identity on the Web of Data

owl:sameAs and rdfs:seeAlso

http://www4.wiwiss.fu-berlin.de/bizer/pub/

LinkedDataTutorial/
owl:sameAs: Used to identify two resources with different

URIs as being the same resource
 rdfs:seeAlso: “More information about this resource can be
found here”
owl:InverseFunctionalProperty

foaf:mbox, foaf:openid, etc. can be used to identify

uniqueness for a foaf:Person
60 of XYZ

Interlinking identities and networks
Digital Enterprise Research Institute www.deri.ie
61 of XYZ

Native export of RDF data
Digital Enterprise Research Institute www.deri.ie
CMS can expose RDF data natively using dedicated

plug-ins
SIOC Export for Drupal: http://drupal.org/project/SIOC

Provide RDF export of each blog post

– http://apassant.net/blog/2009/03/07/call-suggested-
features-sparql-working-group
– http://apassant.net/sioc/node/235
Using RDF autodiscovery feature in the HTML header

– So that RDF can be discovered when browsing HTML
– Semantic Radar: http://sioc-project.org/firefox
RDFa to be included in Drupal7 code !

– http://groups.drupal.org/node/16597
– 100.000’s of RDFa-powered websites
62 of XYZ

Overview: SIOC for vBulletin
Digital Enterprise Research Institute www.deri.ie
63 of XYZ

Translation services
Digital Enterprise Research Institute www.deri.ie
What about data already structured but not in RDF ?

JSON, RSS2.0, bibtex, etc …

Translation services can be used

Triplr:

– http://triplr.org
Babel

– http://simile.mit.edu/babel/
Bibtex (from Bibsonomy) to RDF

http://www.bibsonomy.org/bibtex/

286dc964427792faedb4df90056a6fe98/sirakov
http://simile.mit.edu/babel/translator?

reader=bibtex&writer=rdf-xml&mimetype=default
64 of XYZ

Relational to RDF Mapping
Digital Enterprise Research Institute www.deri.ie
Relational data (RDB) is structured data and can be

mapped to RDF straight-forward
Main issues:

Closed-world vs. open-world modeling

Assigning URIs for entities (records)

Mapping language expressivity

For a state-of-the-art see

http://www.w3.org/2005/Incubator/rdb2rdf/
RDB2RDF_SurveyReport.pdf
65 of XYZ

Relational to RDF Mapping
Digital Enterprise Research Institute www.deri.ie
Standardization

W3C RDB2RDF Incubator Group 2008/2009

Upcoming W3C RDB2RDF Working Group

Current solutions (see state-of-the-art)

D2RQ

– http://www4.wiwiss.fu-berlin.de/bizer/d2rq/
– DBLP in RDF: http://dblp.l3s.de/d2r/
OpenLink’s Virtuoso

– http://www.openlinksw.com/virtuoso/
Triplify

– http://triplify.org
66 of XYZ

Outline
Digital Enterprise Research Institute www.deri.ie
Content

Motivation

What is the Web of Data?

Creating Structured Data

Discovery, Accessing & Querying

Mash-ups & Advanced Topics

67 of XYZ

Discovery, Accessing & Querying
Digital Enterprise Research Institute www.deri.ie
Discovery is the process of starting with a URI and

learn more about the resources that can be
accessed or described through it
In order to access and query data on the Web, one

needs to know WHERE and HOW
WHERE: indexer, search engines, pings

HOW: FYN, sitemaps, voiD (next slide)

68 of XYZ

Discovering RDF data
Digital Enterprise Research Institute www.deri.ie
Simple case: Follow-Your-Nose by dereferencing

URIs (and hence stepwise browsing the RDF graph)
Indexer or crawler may utilize the semantic

sitemaps extension
http://sw.deri.org/2007/07/sitemapextension/
Applications using linked data should use voiD, the

vocabulary of interlinked datasets
http://semanticweb.org/wiki/VoiD
Allows to learn what a dataset is about

Provides quantitative data on interlinking (statistics)

Enables to deliver licensing, provenance and access

information
69 of XYZ

Discovering RDF data
Digital Enterprise Research Institute www.deri.ie
Ping The Semantic Web

http://pingthesemanticweb.com

A repository of RDF data, provides XML feeds of

newly created information
Can be used to build your application without

having to crawl the Web for relevant data
A food-chain for applications on the Web of Data

– http://sunsite.informatik.rwth-aachen.de/Publications/CEUR-
WS//Vol-248/paper11.pdf
E.g. doap:store

– http://doapstore.org
70 of XYZ

PTSW food-chain
Digital Enterprise Research Institute www.deri.ie
71 of XYZ

Storing and querying RDF data
Digital Enterprise Research Institute www.deri.ie
Distributed querying

Important to keep intact the decentralized architecture of

the WWW
Still experimental, can be quite slow

voiD can be used to identify relevant sources to be queried

Storing data locally and querying

Better performances in terms of querying

But need to deal with data replication

PTSW can be used to find which data to store

72 of XYZ

Setup a SPARQL endpoint
Digital Enterprise Research Institute www.deri.ie
Lots of triple-store available on the market

Virtuoso, Sesame, Joseki …

Based on various back-ups (MySQL, dedicated FS …)

We will focus on xAMP solutions with ARC2

Lightweight RDF framework for PHP

http://arc.semsol.org

RDF Store based on MySQL

Only a few lines of code to set-up a repository

– http://helloopenworld.net/www2009/store1/index.phps
Using SPARQL+ to LOAD / UPDATE / DELETE RDF data

– SPARQL being read-only
73 of XYZ

Loading RDF data
Digital Enterprise Research Institute www.deri.ie
SPARQL is a read-only language

SPARUL and SPARQL+ allow to add / modify / delete

RDF data
LOAD <URI> [INTO <URI>]

Will load the RDF data from <URI> into the store before

going into SPARQL querying
LOAD your FOAF files in the RDF store

http://helloopenworld.net/www2009/store1/

E.g. LOAD <http://helloopenworld.net/www2009/data/

apassant.rdf>
– NB: To be done in POST mode
74 of XYZ

SPARQL
Digital Enterprise Research Institute www.deri.ie
SPARQL Protocol and RDF Query Language

“The SQL of the Semantic Web”

Both a protocol and a query language

– RDF data can be queried via REST
Four different query forms

SELECT, CONSTRUCT, ASK, DESCRIBE

We will mainly focus on the first one

SPARQL is based on a graph-matching approach

Retrieve statements that match some patterns in one (or

more) RDF graph(s)
75 of XYZ

SPARQL SELECT
Digital Enterprise Research Institute www.deri.ie
SELECT all people and their name

http://helloopenworld.net/www2009/files/select1.sparql

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?person ?name
WHERE {
?person a foaf:Person ;
foaf:name ?name .
}
76 of XYZ

SPARQL CONSTRUCT
Digital Enterprise Research Institute www.deri.ie
Contruct an RDF graph from other ones

Can be seen as the XSLT of the Semantic Web

http://helloopenworld.net/www2009/files/

construct1.sparql
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX www2009: <http://ex.org/www2009/>
CONSTRUCT { ?person a www2009:attendee .}
WHERE { ?person a foaf:Person . }
77 of XYZ

SPARQL DESCRIBE
Digital Enterprise Research Institute www.deri.ie
Get information about a given resource

DESCRIBE is implementation specific

http://helloopenworld.net/www2009/files/desc1.sparql

DESCRIBE <
http://helloopenworld.net/www2009/data/
apassant.rdf#me>
78 of XYZ

SPARQL ASK
Digital Enterprise Research Institute www.deri.ie
Check if a particular pattern matches the RDF graph

Is Alex a foaf:Person ?

 http://helloopenworld.net/www2009/files/ask1.sparql
PREFIX foaf: http://xmlns.com/foaf/0.1/
ASK { <http://helloopenworld.net/www2009/data/
apassant.rdf#me> a foaf:Person . }
79 of XYZ

SPARQL Protocol
Digital Enterprise Research Institute www.deri.ie
REST-compliant protocol for SPARQL queries

http://helloopenworld.net/www2009/store1/?

query=PREFIX+foaf%3A+%3Chttp%3A%2F%2Fxmlns.com
%2Ffoaf%2F0.1%2F%3E%0D%0ASELECT+%3Fperson+
%3Fname%0D%0AWHERE+{%0D%0A+%3Fperson+a+foaf
%3APerson+%3B%0D%0A+++foaf%3Aname+%3Fname+.%0D
%0A}%0D%0A&output=htmltab
Easy for remote SPARQL querying

SPARCool

Easy SPARQL querying via simple URLs

http://sparcool.net

80 of XYZ

Lightweight inference
Digital Enterprise Research Institute www.deri.ie
ARC2 does not provide RDFS inference engine

But triggers can be used to write one

http://apassant.net/blog/2008/10/01/lightweight-

subpropertyof-subclassof-inference-arc2
Rule rdfs9: inference on subproperties

http://www.w3.org/TR/rdf-mt/#RDFSRules

Can be done with SPARQL CONSTRUCT and ARC2 triggers

http://helloopenworld.net/www2009/store2/index.phps

http://helloopenworld.net/www2009/files/

ARC2_SubPropertyInferenceTrigger.phps
81 of XYZ

Lightweight inference
Digital Enterprise Research Institute www.deri.ie
LOAD your profile in the inference-enabled store

http://helloopenworld.net/www2009/store2

Try the following query in both stores

Only the second one deals with subProperty inference

http://helloopenworld.net/www2009/files/select2.sparql

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?person
WHERE {
<YOUR_URI> foaf:knows ?person .
}
82 of XYZ

Complex triggers
Digital Enterprise Research Institute www.deri.ie
LOAD the RDF file corresponding to each user

interest
Must be done to avoid issues of distributed SPARQL

querying
Trigger designed using SPARQL SELECT + SPARUL

LOAD
For each loaded file, check if there are any

foaf:topic_interest and load them into the store
http://helloopenworld.net/www2009/files/

ARC2_InterestLoadTrigger.phps
http://helloopenworld.net/www2009/store3

83 of XYZ

SPARQL SELECT w/ Triggers
Digital Enterprise Research Institute www.deri.ie
Advanced querying capabilities

http://helloopenworld.net/www2009/files/select3.sparql

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dbo: <http://dbpedia.org/ontology/>
SELECT ?person
WHERE {
?person foaf:topic_interest [
dbo:director <http://dbpedia.org/resource/
Quentin_Tarantino> . ]
}
84 of XYZ

Outline
Digital Enterprise Research Institute www.deri.ie
Content

Motivation

What is the Web of Data?

Creating Structured Data

Discovery, Accessing & Querying

Mash-ups & Advanced Topics

85 of XYZ

Mash-ups & Advanced Topics
Digital Enterprise Research Institute www.deri.ie
Applying and extending what we have learned

Displaying and rendering the Web of Data

End-user Interaction, UI

Read/write Web of Data

86 of XYZ

Exhibit faceted browsing
Digital Enterprise Research Institute www.deri.ie
Exhibit

JavaScript library for faceted browsing

http://www.simile-widgets.org/exhibit/

Can be used directly on the top of a SPARQL

endpoint
Thanks to SPARQL CONSTRUCT and the Babel translation

service
http://helloopenworld.net/www2009/files/

construct2.sparql
http://helloopenworld.net/www2009/exhibit

http://microplanet.sioc-project.org/

– With geolocation services
87 of XYZ

Ubiquity command
Digital Enterprise Research Institute www.deri.ie
Ubiquity

Mozilla Firefox command line for the Web

http://ubiquity.mozilla.com/

Find people that like a given topic when browsing

Wikipedia
(1) Query Dbpedia to find the related URI

(2) Query the RDF Store to identify related people

Total: 2 SPARQL queries !

http://helloopenworld.net/www2009/ubiquity

http://en.wikipedia.org/wiki/Reservoir_Dogs

88 of XYZ

Ubiquity command
Digital Enterprise Research Institute www.deri.ie
89 of XYZ

Mash-ups & Advanced Topics
Digital Enterprise Research Institute www.deri.ie
Enabling the read/write Web of Data with

pushback/RDForms
http://esw.w3.org/topic/
PushBackDataToLegacySources
Using linked data, SPARQL CONSTRUCT for

mapping and a fixed-schema vocabulary called
RDForms http://rdfs.org/ns/rdforms
90 of XYZ

Mash-ups & Advanced Topics
Digital Enterprise Research Institute www.deri.ie
91 of XYZ

Mash-ups & Advanced Topics
Digital Enterprise Research Institute www.deri.ie
View demos at

http://ld2sd.deri.org/pushback/
Check out code at

http://code.google.com/p/pushback/
Join and contribute!

92 of XYZ

Outline
Digital Enterprise Research Institute www.deri.ie
Content

Motivation

What is the Web of Data?

Creating Structured Data

Discovery, Accessing & Querying

Mash-ups & Advanced Topics

93 of XYZ

Conclusion
Digital Enterprise Research Institute www.deri.ie
Web of Data is a reality

Tons of tools and technologies exist to

Create and describe data on the Web

Store and access data on the Web

Discover and query data on the Web

Challenges

Technical issues such as scalability and usability

Social issues (trust, privacy, etc.)

Economic issues (building a critical mass)

– For example Obama administration using SIOC and linked
data is fairly motivating
94 of XYZ

Events
Digital Enterprise Research Institute www.deri.ie
LDOW2009

http://events.linkeddata.org/ldow2009/

Today, will continue this afternoon

Gathering tonight with the LOD community !

ESWC and ISWC

Major venues for research on the Semantic Web

Triplification challenge

http://triplify.org/Challenge/2009

Deadline 30 May

95 of XYZ

Feedback
Digital Enterprise Research Institute www.deri.ie
Did you learn something during the tutorial ?

Do you think you can now explain the Web of Data

and build applications ?
Which topics that you expected were not covered ?

Feel free to discuss or contact us

alexandre.passant@deri.org

michael.hausenblas@deri.org

#swig on irc.freenode.net

96 of XYZ