Hello Open World - Semtech 2009

Digital Enterprise Research Institute www.deri.ie

Hello Open Data World!
The Web of Data for the Pragmatic Developer
Alexandre Passant & Giovanni Tummarello
SEMTECH, San Jose, California 2009

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

NB: Tutorial adapted from the WWW2009 “Hello Open
World” presentation by Alexandre Passant and Michael
Hausenblas

2

Speakers introduction

 Alexandre Passant
 Postdoctoral researcher, DERI Galway
 Social Software and Semantic Web
 http://apassant.net

 Giovanni Tummarello
 Research Fellow, DERI Galway
 Web of Data Search and Mashups
 http://g1o.net

3

DERI Galway

 Enabling Networked Knowledge
 Social Semantic Information Spaces
 Semantic Reality
 Approximately 130 people

4

Companion website

http://helloopenworld.net

5

What is this tutorial about

 What you will learn
 Web of Data principles
 Architecture principles for applications on the Web of Data
 Finding and creating structured data
 Using vocabularies and lightweight inference
 Querying Web data with SPARQL and with Sindice
 User interfaces and mash-ups
 What you will not
 Ontology mapping and alignment
 Advanced rules languages
 Complex SPARQL querying

6

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
 Join the Web of Data
 Effectively enriching your existing pages and applications with
annotations that will help your data to be found and integrated
 Leverage the Web of Data for your apps
 Finding data “out there” and reusing it
 Using open-source and xAMP technologies
 Creating, consuming and mashing-up RDF data

7

Outline

 Content
 Motivation

8

Motivation

Yahoo

Google
Rich
Snippets

9

Motivation

 More and more data is available on the Web
 Structured data, in RDF, microformats, etc.
 Reusing Data is a value for your application !
 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)
 Enables serendipitous usage of data

10

Outline

 Content
 Motivation

11

What is the Web of Data?

 Web of information structured via standards and made
available on the Web
 Microformats and GRDDL
 RDF using various serializations: RDF/XML, RDFa, etc.

12

RDF

 RDF: Resource Description Framework
 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
 predicate
 object
<http://sw-app.org/#i><http://xmlns.com/foaf/0.1/knows>
<http://apassant.net/alex>.

13

RDF

14

RDF

@prefix dcterms: <http://purl.org/dc/terms/> .

<http://deri.ie/teaching/tutorials/lod-intro>
dcterms:title “Tutorial on Linked Data - A Practical Introduction” ;
dcterms:author<http://sw-app.org/mic.xhtml#i> ;
dcterms:subject <http://dbpedia.org/resource/Linked_Data> .

15

“Semantic Data” on the Web

 Web of Data == the Semantic Web?
 Not really, it’s the “Web” facing part of it
 It’s part of it, a kind of subset
 In contrast to the full-fledged Semantic Web vision, the Web
of Data more about raw data publishing in interoperable
format than about logic inference and reasoning on it

16

What is the Web of Data?

17

Web of data via “Linked Data”

 Linked data principles, by Tim Berners-Lee, ca. 2006
 Use URIs to identify things (anything, not just documents)
– “To benefit from and increase the value of the World Wide Web,
agents should provide URIs as identifiers for resources”
– http://www.w3.org/TR/webarch/
 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
 Example http://dbpedia.org/resource/Dublin

18

Linked data growth

2007

2008

19

Linked data growth

2008

2009

20

Needed: shared vocabularies (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

21

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 !

22

Notable ontologies

 Social networks and social data
 FOAF – Friend Of A Friend
 SIOC – Semantically-Interlinked Online Communities
 Software development
 DOAP – Description Of A Project
 BEATLE - Bug And Enhancement Tracking LanguagE
 Comprehensive / Top-level
 Yago (From Wikipedia)
 OpenCYC
 Taxonomies
 SKOS – Simple Knowledge Organisation System

23

Zooming in: FOAF Ontology

 A model to describe people and social networks
 http://foaf-project.org
 Concepts
 Person, OnlineAccount, Document, etc.
 Properties
 name, homepage, holdsAccount, knows, etc.

24

FOAF in use

 Google Social Graph API
 http://code.google.com/intl/fr/apis/socialgraph/
 Uses FOAF information already there on the Web to find
your contacts
 http://socialgraph-
resources.googlecode.com/svn/trunk/samples/findcontacts.html
 E.g.: http://apassant.net
– http://socialgraph-
resources.googlecode.com/svn/trunk/samples/findcontacts.html?q=
http%3A%2F%2Fapassant.net
– Contacts found in various FOAF files that link to myself and to my
profile

25

Zooming in: SIOC Ontology

 Describe Web communities and their social interactions
 Who’s writing what, who’s answering who, etc.
 A simple model to ensure easy-integration into existing
applications
 Lightweight: one core ontology, 4 modules
 Plug-ins /core-feature for several CMS
 Drupal, Wordpress etc.
 Enables interoperability between social applications
 http://sioc-project.org

26

The SIOC ontology

 The main classes and properties are:

27

Combining FOAF + SIOC

28

Adoption of SIOC

29

Which ontologies to use ?

 SearchMonkey Vocabularies
 http://developer.yahoo.com/searchmonkey/smguide/profile_voca
b.html

30

Which ontologies to use ?

 How to Publish Linked Data on the Web
 http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/

31

Extending ontologies ?

 What if existing ontologies are not enough for your
needs ?
 Create a new one
 … or extend existing ones !
 Ontologies can be extended in a decentralized way
 E.g. you can create a subproperty of foaf:knows,
“attendedTutorialWith”, in your own ontology
 Publish in on your own
 Or use http://open.vocab.org

32

Attention: Domain and range

 Domain and range of properties are descriptive, not
prescriptive
 Example if we say :father rdfs:domain :Person
– Not only pre-defined Persons can be fathers
– But every father is a Person !
 Consequence 1: One triple is enough to describe several
informations
 Consequence 2: DON’T use foaf:homepage for a shoe
 For details
 Based on RDF semantics (Rule rdfs2)
 http://www.w3.org/TR/rdf-mt/

33

Linking Open Data Project

 Community project with W3C support started in early
2007 [LOD]: http://linkeddata.org
 Idea: take existing (open) data sets and make them
available on the Web in RDF
 Interlink them with other data sets
 Expand the network effect of Linked Data !
 Raw Data Now !
 Tim Berners-Lee TED talk
 http://www.ted.com/index.php/talks/tim_berners_lee_on_the_nex
t_web.html
Kudos to Tom Heath and Richard Cyganiak; the material in
this section is heavily based on their work.

34


May 2007

35


Feb 2009

36

Notable datasets of the LOD cloud

 Linking Open Data
 Community project started in 2007 - http://linkeddata.org
 Dbpedia – http://dbpedia.org
 Wikipedia in RDF: “more than 2.6 million things, including at
least 213,000 persons, 328,000 places, 57,000 music albums,
36,000 films, 20,000 companies”
 Geonames – http://geonames.org
 “over eight million geographical names”: coordinates, etc.
 Freebase - http://rdf.freebase.com/
 “5203825 Topics 14110006 Named Entities”
 E.g. http://rdf.freebase.com/rdf/en.blade_runner

37


DBpedia

38


Geonames

39

Querying dbpedia

 Programmatically (via SPARQL, see later)
 Via User Interface
 http://wikipedia.aksw.org

40

Tools and Applications

 Linking Open Data homepage [LOD] has
 Browsing with Tabulator, VisiNav, Sig.ma, 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/Community
Projects/LinkingOpenData/Applications

41

Tools and Applications

DBpedia Mobile

42

Applications integration

BBC music beta

43

Typical architectures of applications
for the Web of Data (1/2)

from: Heitmann, B., et al., “Towards a reference architecture for Semantic Web
applications,” Proceedings of the 1st Int. Web Science Conference, 2009

44

Typical architectures of applications
for the Web of Data (2/2)

 Data Interface: Abstraction layer regarding implementation,
number and distribution of persistence layers.
 Persistence Layer: Persistent storage of data and run time state.
 User Interface: Human accessible interface for using application
and viewing data. (“read-only”)
 Annotation User Interface: Edit, create, import or export data.
 Integration Service: Merge Structure, Syntax or Semantics of data
from multiple heterogeneous sources.
 Search Engine: Search on content or semantic features.
 Crawler: Retrieval of remote data for integration service.

45

Outline

 Content
 Motivation
 What is the Web of Data?

46

Creating Structured Data

 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
– For both human and machines !
 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

47

Getting a FOAF profile

 Or how to give yourself a URI
 Be part of the Web of Data
 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)
 I already have an homepage, what about duplication of
information ?
 Use RDFa to embed RDF annotations in yourhomepage !
 More on thistopic in a few slides

48

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/semtech09/data
 You finally got a URI !
– http://helloopenworld.net/semtech09/data/apassant.rdf#me

49

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

50


51


52

RDFa and GRDDL

 GRDDL is a mechanism to transform any kind of XML to
RDF
 XHTML+RDFa is XML, hence GRDDL can extract it
 Simply embeds RDFa annotations in your HTML code
 Indexed by Yahoo! SearchMonkey and Google
 Done via XSLT, available at http://www.w3.org/2008/07/rdfa-xslt

53

RDFa and GRDDL

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

54

RDFa and GRDDL

 http://sdow2009.semanticweb.org

55

RDFa and GRDDL

 Browse source to check RDFa annotations

56

RDFa and GRDDL

 Header contains prefixes and links to the GRDDL transformation

57

RDFa and GRDDL

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

58

AddRDFa to yourhomepage

 Choose the right DTD
 http://www.w3.org/TR/rdfa-syntax/DTD/xhtml-rdfa-1.dtd
 Addprefixesdefinition in the header
 Depending on ontologies youwill use
 Addappropriate profile
 E.g. http://ns.inria.fr/grddl/rdfa/
 Addaditionalmarkup
 E.g. rel, about, typeof

 Example
 http://helloopenworld.net/semtech2009/files/profile.html

59

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

60

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

61

RDFification services

 Translates many structured sources into RDF
 URIBurner
– http://linkeddata.uriburner.com/
– Open Source, C++ , Based on Virtuoso
 Any23
– Sindice sponsored
– Open Source, Java based
 Swignition
– http://buzzword.org.uk/swignition/
– Perl based
 Triplr
– Purelysyntactic, fast
– http://triplr.org

62

Interlinking identities

 The previous exporters create different URIs
 A need to unify your online identity on the Web of Data
 owl:sameAs
 Used to state that two resources with different URIs are about
the same entitiy
 http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/
 owl:InverseFunctionalProperty
 foaf:mbox, foaf:openid, etc.
 “Inverse Functional” properties can be used to identify
uniqueness for a foaf:Person

63

Interlinking identities and networks

64

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 core !
– http://groups.drupal.org/node/16597
– 100.000’s of RDFa-powered websites

65

Overview: SIOC for vBulletin

66

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_Su
rveyReport.pdf

67

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

68

Outline

 Content
 Motivation
 Creating Structured Data

69

Discovery of RDF data

 Discovery is the process of starting with a URI and learn
more about the resources that can be accessed or
described through it
 .. Without using a search engine

70

Discovering RDF data

 Simple case: Dereference
 “Follow-Your-Nose” approach
 Semantic Sitemaps
 to find SPARQL endpoints or data dumps
http://sw.deri.org/2007/07/sitemapextension/
 Links from within the RDF
 voiD, vocabulary of interlinked datasets
– Allows to learn what a dataset is about
– Provides quantitative data on interlinking (statistics)
– Enables to deliver licensing, provenance and access information
– http://semanticweb.org/wiki/VoiD
 SeeAlso, owl:import or simply dereference other URIs

71

Semantic Web Sitemaps

 Easy to create metadata from your existing database
(D2RQ, microformats etc)
 But you need to tell the world about it!
 More is needed to make your data useful (e.g. linking to OTHER
URIs if your entities are not something completely “yours”)
 Need to make the world know your data is there.
 Semantic Web Sitemaps can help

72

Large quantities of linked data: how to
expose?

 The fact that the data is HTTP retrievable in small bits
makes it crawlable.
 But data producers are very scared of this:
 Million of hits for each refresh
 And clearly something better must be possible
 Most data producers do in fact already provide full dumps of the
base data
 Or SPARQL endpoints

73

Extending Sitemaps to expose data

 Sitemaps:
 Originally by Google, immediately adopted by all (Yahoo, MSN)
etc
 Expose the “deep web”, by providing a list of pages “to be
crawled”
 Written in XML, Linked directly in the robot.txt
Example:
<?xml version="1.0" encoding="UTF-8"?>
< urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
< url>
< loc>http://www.example.com/</loc>
< lastmod>2005-01-01</lastmod>
< changefreq>monthly</changefreq>
< priority>0.8</priority>
</url>
</urlset>

74

The Semantic Sitemap Extention

Example first:

<urlset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9
http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd"
xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
xmlns:sc="http://sw.deri.org/2007/07/sitemapextension/scschema.xsd">

<sc:dataset>
<sc:datasetLabel>Product Catalog for Example.org</sc:datasetLabel>
<sc:dataDumpLocation>http://example.org/cataloguedump.rdf
</sc:dataDumpLocation>
<sc:linkedDataPrefix>http://example.org/products/</sc:linkedDataPrefix>
<changefreq>monthly</changefreq>
</sc:dataset>

</urlset>

75


Example first:


<sc:dataset>
</sc:dataset>

</urlset>

76


Example first:


<sc:dataset>
</sc:dataset>

</urlset>

77


Example first:


<sc:dataset>
</sc:dataset>

</urlset>

78


Example first:


<sc:dataset>
</sc:dataset>

</urlset>

79


Example first:


<sc:dataset>
</sc:dataset>

</urlset>

80

How it is meant to be used

 As a crawler
 If you are given a URL for an RDF site check for the sitemap
 If a dump is available, download that instead

 As a client
 If you have a dump, and want an update
 Check the sitemap, to locate it in case it has changed position
 Or to locate a SPARQL endpoint

81

Or Search!

 Sindice Search Engine
 http://sindice.com
 Look up by RDF by keywords and on property/value
descriptions
 Simple queries but executed fast.
 Fast indexing (20 to 60m) of newly “pinged” information
 Sindice can be thought as a “Spider In the middle” for application
2 application semantic communication via published data.

82

Searching the Web of Data

 E.g. search for people who claim to know X

83

Lod.openlinksoftware.com

 Query service over all the major “linked dataset”
 Advanced queries, (SPARQL, see later)
 No pings
 In general best effort results due to timeouts (on non
simple queries)

84

How to manipulate and query RDF?

 Querying Web data on runtime
 Needs to load RDF data in memory, can be quite slow
 Storing information in RDF-stores and using SPARQL
 Involves data replication and need to sync between data from the
Web and data in your RDF-store
– Sindice API to help syncing
 Lots of RDF-stores available on the market
– Sesame
– Jena
– Openlink Virtuoso
– Allegrograph
– OpenAnzo
– Mulgara, etc

85

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): independant from serialization
 W3C SPARQL WG currently working on new features
 http://www.w3.org/2009/01/sparql-charter

86

SPARQL SELECT

 SELECT all people and their name
 http://helloopenworld.net/semtech2009/files/select1.sparql

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?person ?name
WHERE {
?person a foaf:Person ;
foaf:name ?name .
}

87

SPARQL CONSTRUCT

 Contruct an RDF graph from other ones
 Can be seen as the XSLT of the Semantic Web
 http://helloopenworld.net/semtech2009/files/construct1.sparql

PREFIX semtech09: <http://ex.org/semtech09/>
CONSTRUCT { ?person a semtech09:attendee .}
WHERE { ?person a foaf:Person . }

88

SPARQL DESCRIBE

 Get information about a given resource
 DESCRIBE is implementation specific and can return
different results depending on the triple-store used
 http://helloopenworld.net/semtech2009/files/desc1.sparql

DESCRIBE
<http://helloopenworld.net/semtech2009/data/apassant.r
df#me>

89

SPARQL ASK

 Check if a particular pattern matches the RDF graph
 Is Alex a foaf:Person ?
 http://helloopenworld.net/semtech2009/files/ask1.sparql

PREFIX foaf: http://xmlns.com/foaf/0.1/
ASK {
<http://helloopenworld.net/semtech2009/data/apassant.r
df#me> a foaf:Person . }

90

SPARQL Protocol

 REST-compliant protocol for SPARQL queries
 http://helloopenworld.net/semtech2009/store1/?query=PREFIX+f
oaf%3A+%3Chttp%3A%2F%2Fxmlns.com%2Ffoaf%2F0.1%2F
%3E%0D%0ASELECT+%3Fperson+%3Fname%0D%0AWHER
E+{%0D%0A+%3Fperson+a+foaf%3APerson+%3B%0D%0A++
+foaf%3Aname+%3Fname+.%0D%0A}%0D%0A&output=htmlta
b
 Easy for remote SPARQL querying

91

SPARCool.net

 http://sparcool.net
 Run SPARQL queries on any URI thatfollows the Linked
Data principles
 http://sparcool.net/j/dbp:abstract;l=en/http://dbpedia.org/resource
/Semantic_Web
 Various formats for results (HTML, JSON, etc.)
 Embedresults in your documents using JSONP

92

Setup a SPARQL endpoint

 Various open-source triple-store availables
 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/semtech2009/store1/index.phps
 Using SPARQL+ to LOAD / UPDATE / DELETE RDF data
– SPARQL being read-only
 Used in various of our projects
– SMOB, LODr, etc

93

Loading RDF data

 SPARQL is a read-only language
 SPARQL+ allows 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/semtech2009/store1/
 E.g. LOAD
<http://helloopenworld.net/semtech2009/data/apassant.rdf>
– NB: To be done in POST mode

94

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/semtech2009/store2/index.phps
 http://helloopenworld.net/semtech2009/files/ARC2_SubPropertyInfe
renceTrigger.phps

95

Lightweight inference

 LOAD your profile in the inference-enabled store
 http://helloopenworld.net/semtech2009/store2
 Try the following query in both stores
 Only the second one deals with subProperty inference
 http://helloopenworld.net/semtech/2009/files/select2.sparql
SELECT ?person
WHERE {
<YOUR_URI>foaf:knows ?person .
}

96

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
 http://helloopenworld.net/semtech2009/files/ARC2_InterestLoad
Trigger.phps
 http://helloopenworld.net/semtech2009/store3

97

SPARQL SELECT w/ Triggers

 Advanced querying capabilities
 http://helloopenworld.net/semtech2009/files/select3.sparql
PREFIX dbo: <http://dbpedia.org/ontology/>
SELECT ?person
WHERE {
?person foaf:topic_interest [
dbo:director<http://dbpedia.org/resource/Quentin_Tarantino
>.]
}

98

Outline

 Content
 Motivation
 Discovery, Accessing & Querying

99

Mash-ups & Advanced Topics

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

100

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
 http://helloopenworld.net/semtech2009/files/construct2.sparql
 http://helloopenworld.net/semtech2009/exhibit
 http://microplanet.sioc-project.org/
– With geolocation services

101

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/semtech2009/ubiquity
 http://en.wikipedia.org/wiki/Reservoir_Dogs

102

Ubiquity command

103

Mash-up tools

 DERI Pipes, a tool for semantic mashups
 http://pipes.deri.org

104

Sig.ma Mashup Maker

 Web of data comes together
 In an interactive mashup maker
 Mashups can be embedded or queries programmatically

105

Geolocation mash-ups

 Since data is interlinked, it’s easy to combine it
 Can mix personal and public data, e.g. in organisations

106

Data directories

 http://doapstore.org
 A directory of Software projectsdescribedwith DOAP
 CompletelyRDF-based

107

Ongoing works

 Enabling the write on the Web of Data
 “Pushback”
http://esw.w3.org/topic/PushBackDataToLegacySources
 More demos at: http://ld2sd.deri.org/pushback/
 Check out code at
http://code.google.com/p/pushback/ and contribute !
 Using RDFa to automate web forms
 RDFormshttp://rdfs.org/ns/rdforms

108

Outline

 Content
 Motivation
 Discovery, Accessing & Querying
 Mash-ups & Advanced Topics

109

Conclusion

 Web of Data is a reality
 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
 Build and expand your applications with data on the Web
 Challenges
 Technical issues such as scalability and usability
 Social issues (trust, privacy, etc.)
 Economic issues (building a critical mass)

110

Events

 LDOW Series
 http://events.linkeddata.org/
 ESWC and ISWC
 Major venues for academic research on the Semantic Web
 SFSW: Scripting For the Semantic Web Workshop
– http://www.semanticscripting.org/
 Triplification challenge
 Applications enabling existing systems being part of the Web of
Data
 http://triplify.org/Challenge/2009
 Deadline June 30th, 2009

111

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
 giovanni.tummarello@deri.org
 michael.hausenblas@deri.org
 #swig on irc.freenode.net

112

Hello Open World - Semtech 2009

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