Hello Open World - The Web of Data for the Pragmatic Developer

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

Content
 
Motivation
 
What is the Web of Data?
 
Creating Structured Data
 
Discovery, Accessing & Querying
 
Mash-ups & Advanced Topics
 

2

Speakers introduction

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

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

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

Content
 
Motivation
 
 
 
 
 

6

Motivation

2007

2008

7

Motivation

2008

2009

8

Motivation

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

Content
 
Motivation
 
 
 
 
 

10


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


12


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


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

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


A Uniform Resource Identifier (URI) is a compact
 
sequence of characters that identifies an abstract
or physical resource as of RFC3986
Syntax
 
URI = scheme quot;:quot; hier-part [ quot;?quot; query ] [ quot;#quot; fragment ]
Example
 
foo://example.com:8042/over/there?name=ferret#nose
_/ _________________/_________/ __________/ __/
| | | | |
scheme authority path query fragment

16


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


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

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


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


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


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 quot;Accept: application/rdf+xmlquot; http://dbpedia.org/resource/Galway
HTTP/1.1 303 See Other
Content-Type: application/rdf+xml
Location: http://dbpedia.org/data/Galway.rdf

22


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


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

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

26

What is the Web of Data? - Ontologies

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
 

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What is the Web of Data? - Ontologies

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

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What is the Web of Data? – Open World

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

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What is the Web of Data? – Open World

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

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What is the Web of Data? - Overview

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


32


33


34

Applications for the Web of Data

Towards a reference architecture for Semantic Web applications.
Heitmann et al. (WebSci09 – http://journal.webscience.org/199/)

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Linking Open Data Project

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


May 2007

37


Feb 2009

38


DBpedia

39


Geonames

40

Tools and Applications

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


DBpedia Mobile

42


BBC music beta

43

Outline

Content
 
Motivation
 
 
 
 
 

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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

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Getting a FOAF profile

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)
 

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Extend your FOAF profile

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

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Defining personal interests

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

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Extending a vocabulary

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
 

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RDFa and GRDDL

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

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RDFa and GRDDL

The GRDDL Primer at
 
http://www.w3.org/TR/grddl-primer/#scheduling
shows the overall processing of XHTML+RDFa:

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RDFa and GRDDL

http://sdow2009.semanticweb.org
 

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RDFa and GRDDL

 
Browse source to check RDFa annotations
 

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RDFa and GRDDL

 
Header contains prefixes and links to the GRDDL
 
transformation

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RDFa and GRDDL

 
Webpage can be translated to native RDF/XML using an
 
RDFa distiller - http://www.w3.org/2007/08/pyRdfa/

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Wrappers for existing sources

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
 

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Wrappers for Web 2.0 services

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

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Interlinking identities

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

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Interlinking identities and networks

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Native export of RDF data

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

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Overview: SIOC for vBulletin

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Translation services

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

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Relational to RDF Mapping

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

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Relational to RDF Mapping

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

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Outline

Content
 
Motivation
 
 
 
 
 

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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)
 

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Discovering RDF data

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

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Discovering RDF data

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

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PTSW food-chain

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Storing and querying RDF data

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
 

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Setup a SPARQL endpoint

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

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Loading RDF data

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

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SPARQL

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)

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SPARQL SELECT

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 .
}

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SPARQL CONSTRUCT

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 www2009: <http://ex.org/www2009/>
CONSTRUCT { ?person a www2009:attendee .}
WHERE { ?person a foaf:Person . }

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SPARQL DESCRIBE

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>

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SPARQL ASK

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 . }

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SPARQL Protocol

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
 

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Lightweight inference

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
 
 
ARC2_SubPropertyInferenceTrigger.phps

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Lightweight inference

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
 
 

SELECT ?person
WHERE {
<YOUR_URI> foaf:knows ?person .
}

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Complex triggers

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
 
ARC2_InterestLoadTrigger.phps
http://helloopenworld.net/www2009/store3
 

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SPARQL SELECT w/ Triggers

Advanced querying capabilities
 
 

PREFIX dbo: <http://dbpedia.org/ontology/>
SELECT ?person
WHERE {
?person foaf:topic_interest [
dbo:director <http://dbpedia.org/resource/
Quentin_Tarantino> . ]
}

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Outline

Content
 
Motivation
 
 
 
 
 

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Applying and extending what we have learned
 
Displaying and rendering the Web of Data
 
End-user Interaction, UI
 
Read/write Web of Data
 

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Exhibit faceted browsing

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
 
construct2.sparql
http://helloopenworld.net/www2009/exhibit
 
http://microplanet.sioc-project.org/
 
–  With geolocation services

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Ubiquity command

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
 

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Ubiquity command

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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

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View demos at
 
http://ld2sd.deri.org/pushback/
Check out code at
 
http://code.google.com/p/pushback/
Join and contribute!
 

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Outline

Content
 
Motivation
 
 
 
 
 

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Conclusion

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

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Events

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
 

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Feedback

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
 

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Hello Open World - The Web of Data for the Pragmatic Developer

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