Introduction to the Semantic Web

Tomasz Pluskiewicz PGS Software
INTRODUCTION TO
THE SEMANTIC WEB
2012-11-28
Introduction to the Semantic Web 1

Agenda
 What is the Semantic Web?
 What is data in the Semantic Web?
 Storing and publishing semantic data
 Querying the Semantic Web
 What is there for developers?
 How does the Semantic Web compare?
 So who actually does the Semantic Web?
2012-11-28Introduction to the Semantic Web
2

What is the Semantic Web?
2012-11-28
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Introduction to the Semantic Web

What is the Semantic Web?
 Semantics = meaning (from Greek)
 Set of practices and standards
 Synonymous or related to:
 Web of data
 Linked data (cloud)
 Giant Global Graph (GGG)
 Web 3.0
 Open Data
 Big Data
4

So what is it about?
 Allowing machines to understand data
 Ease sharing and mixing data
 Extend the World Wide Web rather than
replace it
5

Little bit of history
 1969: paper Semantic Information Processing
by Ross Quillial
 1980s: CYC and WordNet
 mid- to late 1990s: Tim Berners-Lee coins the
term Semantic Web
 Today: dbpedia: 1.2m triples
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Semantic Web building blocks
7

Representation
The basics of semantic data
2012-11-28
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It’s all about resources
 Extensive use of URIs (and most often URLs)
 (Almost) everyting is a URI
 Example URIs:
 http://infusion.com/people/tpluskiewicz
 urn:isbn:1898432023
 http://xmlns.com/foaf/0.1/firstName
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It’s all findable about resources
2012-11-28
 Identifier
 Representation
 Resource itself
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 URI (URL?)
 HTML, RDF
 Described object
Identifier URI should be different than the representationURI
Identifiers should not change

Cool URIs
 Resource and representation have different
URIs
 Hash URIs
 http://www.example.com/about#alice
 http://www.example.com/about.html
 „Normal” URIs
 http://www.example.com/id/bob
 http://www.example.com/people/bob.html
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Resource Description Format
 Facts and relations organized in triples
 Triples mimic natural language sentences
 Graphical representation is a directed graph
My name is Tomasz Pluskiewicz.
My age is 26.
I work for PGS Software.
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Resource Description Framework
ex:tpluskiewicz
15
Tomasz
Pluskiewicz
26
foaf:fullName
ex:PGS-
Software

Serializing RDF triples
2012-11-28
 RDF/XML (.rdf)
 Notation3 (.n3)
 N-Triples (.nt)
 Turtle (.ttl)
 JSON-LD
 TriG (.trig)
 TriX (.trix)
 application/rdf+xml
 text/n3
 text/plain
 text/turtle
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Format MIME type

RDF/XML vs Turtle
2012-11-28
 Difficult to author
 Verbose
 No cannonical
serialization
 Simple
 Concise
 Has means of
further compressing
content
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RDF/XML Turtle

There can be multiple graphs
 Sets of triples form graphs
 Graphs can be named with a URI
 Named graph are also resources, hence there
can be triples describing those graphs
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Adding meaning
The basics of semantic data
2012-11-28
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Basics of RDF(S) resources
2012-11-28
 rdfs:Resource
 rdfs:Class
 rdfs:Property
 rdfs:Datatype
 rdfs:Literal
 rdf:type
 rdfs:label
 rdfs:subClassOf
 rdfs:subPropertyOf
 rdfs:range
 rdfs:domain
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classes properties

Web Ontology Language
 OWL: Lite, DL and Full
 OWL 2: EL, QL and RL
 Defining constraints
 Enables defining complex rules
 Uses specialized syntaxes
 Base terms: owl:Thing, owl:Nothing,
owl:DatatypeProperty, owl:ObjectProperty,
owl:sameAs
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Common ontologies
 Friend of a Friend
 Dublin Core
 SIOC
 SKOS
 UMBEL
 Suggested Upper Merged Ontology
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 Geonames
 BIBO

Specialized ontologies
 Gene Ontology
 GOLD (General O. for Linguistic Description)
 Foundational Model of Anatomy
 GoodRelations
 Lexvo
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Storing and publishing
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Storing in relational databases
 Mapping tables to triples:
 D2RQ
 R2RML
 Ultrawrap
 Using RDBMS with RDF built-in capabilities
 Oracle 11g
 Virtuoso
 Jena SDB
 IBM DB2
27

Native triplestores
 Using native triple (quad) stores
 Virtuoso
 AllegroGraph
 BigOWLIM
 Jena TDB
 4store
 Stardog
 Dydra
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Publishing data easily
 Embedding semantic markup in HTML
 Microformats
 Microdata
 RDFa
 Directly publishing RDF documents
http://manu.sporny.org/2011/uber-comparison-rdfa-md-uf/
29

Microformats example
2012-11-28
<ul>
<li>
Joe Doe</li>
<li>
The Example Company
</li>
<li>
604-555-1234</li>
<li>
<a>
Website</a>
</li>
</ul>
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<ul class="vcard">
<li class="vcard">
Joe Doe</li>
<li class="org">
The Example Company
</li>
<li class="tel">
604-555-1234</li>
<li>
<a class="url">
Website</a>
</li>
</ul>

Microdata example
<section itemscope itemtype="http://data-vocabulary.org/Person">
Hello, my name is John Doe,
I am a graduate research assistant
at the University of Dreams.
My friends call me Johnny.
You can visit my homepage at
<a href="http://www.JohnnyD.com"
itemprop="url">www.JohnnyD.com</a>.
<section itemprop="address" itemscope
itemtype="http://data-vocabulary.org/Address">
I live at 1234 Peach Drive
Warner Robins ,
Georgia.
</section>
</section>
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RDFa example

In his latest book
<cite property="dc:title">Wikinomics</cite>,
Don Tapscott
explains deep changes in technology, demographics and business.
The book is due to be published in
October
2006.

32

Publishing queryable data
 SPARQL Protocol and RDF Query Language
 Remote queries through SPARQL Endpoints
 SPARQL 1.1 features:
 ASK, SELECT, DESCRIBE, CONSTRUCT
 Aggregates
 Federated queries
 Extensibilty, XPath, subqueries
 SPARQL Update
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SPARQL Examples
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SPARQL + rules = SPIN
 SPARQL Inferencing
 Developed by TopQuadrant
 Components of SPIN:
 Represent SPARQL queries as RDF triples
 Allow modularizing queries with spin:Function and
spin:Template
 spin:MagicProperty
 ASK to create constraints
 CONSTRUCT to create rules
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Constraints and rules
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Functions and templates
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What is there for developers?
 dotNetRDF
 Jena/ARQ
 Rdflib
 RDF.rb
 EasyRdf
 Rdfquery
 Redland
 (Web)Protégé
 TopBraid Composer
 NeOn
 OntoWiki
 Semantic MediaWiki
 Cubic Web
Programming tools Design tools and frameworks

Semantic Web vs X
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Semantic Web vs XML
2012-11-28
 Data representation
(model)
 Graph
 xsd and XPath
 Schema defined with
RDFS or OWL
 URI identifiers
 Data serialization
(syntax)
 Tree
 xsd and XPath
 DTD or XML schema
 No built-in identifiers
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Semantic Web (RDF) XML

Semantic Web vs REST
2012-11-28
 URIs identify resources
 HTTP encouraged to
allow dereferencing
 Uniform RDF messages
 Resources are linked
(triples)
 Application specific
 Resource Identification
 Uniform Interface
 Self-Describing
Messages
 Hypermedia Driving
Application State
 Stateless Interactions
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Semantic Web REST

Semantic Web vs RDBMS
2012-11-28
 SPARQL
 Felxible and extensible
schema
 Easy data distribution
 Depends on vendor
 Easier process BI
 Open World
 SQL
 Schema must be defined
first and is rather rigid
 Painful replication
 ACID Transactions
 Strict ETL
 Closed World
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Semantic Web Relational databases

Semantic Web vs NoSQL
2012-11-28
 SPARQL
 Graph
 Schemaless
 Named graphs
 Built on standards and
interoperability
 Can seem scientific and
complicated
 Various APIs
 Graph, doc, key-value
 Schemaless
 Documents (doc DBs)
 Tackle specific problems
(latency, scale, perf.)
 Designed for easy
adoption
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Semantic Web NoSQL

Who actually does the Semantic Web?
Is it happening?
2012-11-28
46

Linked data and open data
 Dbpedia
 Freebase
 Geonames
 Social data
 Media
 Government data
 Publications
 Many many other
 datahub.io
 lod.openlinksw.com
 data.gov
 data.gov.uk
 datadotgc.ca
 openlibrary.org
 bnb.data.bl.uk
http://richard.cyganiak.de/2007/10/lod/lod-datasets_2011-09-19_colored.html

Who does the Semantic Web?
2012-11-28
 IBM DB2
 Open Services
Lifecycle
Collaboration
 Linked Data
Platform
 Oracle 11g
 Triplestore
 Reasoner
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IBM Oracle

2012-11-28
 Webmaster tools
 Knowledge graph
 Freebase
 RDFa/Microdata
(also Yahoo)
 Open Graph
Protocol
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Google Facebook

2012-11-28
Thousands of datasets
Some offered in RDF
Linked by Linking Open
Government Data project
(200 datasets)
Open Government
Partnership (50+
countries)
 Gene research
 Language
processing
 Semantic MediaWiki
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Government/public data Academic work

Where to learn in person?
 Semantic Technology & Business Conference
 Berlin, London, New York, San Francisco
 European Semantic Web Symposium
 International Semantic Web Conference
 International World Wide Web Conference
 International Conference on Semantic Web
and Web Services
 Semantic Web Applications and Tools for Life
Sciences
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Some interesting links...
 http://semanticweb.com/
 http://patterns.dataincubator.org/book/
 http://www.w3.org/standards/semanticweb/
 http://spinrdf.org
 Wikipedia
 http://semanticweb.com/breaking-into-the-nosql-conversation_b27146
 http://gigaom.com/2012/03/11/is-big-data-new-or-have-we-forgotten-its-old-
heroes/
 http://www.snee.com/bobdc.blog/2012/10/sparql-and-big-data-and-
nosql.html
 http://dret.net/netdret/docs/soa-rest-www2009/rest
 http://www.mkbergman.com/
 http://www.cambridgesemantics.com/semantic-university
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...and some books
 David Wood, Linked Data, Manning
 Bob DuCharme, Learning SPARQL, O’Reilly
 Toby Segaran, Programming the Semantic Web, O’Reilly
 John Hebeler, Semantic Web Programming, Wiley
 David Siegel, Pull: The Power of the Semantic Web to Transform Your
Business, Portfolio
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