This document provides an overview of semantic web technologies including the Resource Description Framework (RDF), which is a standard model for data interchange on the web. It describes RDF concepts like triples, graphs, and syntaxes like RDF/XML and Turtle. It also covers ontologies, SPARQL for querying RDF data, linked data, and tools for working with RDF and semantic web technologies.

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Semantic Web introduction

• 1.
  IntroductionSemantic Web & Linked Data
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  Resource Description Framework● W3C standard since 1999● Graph data model● Triples (graph elements) ● Subject: resource URI ● Property: resource URI ● Object: resource URI or literal value● Multiple syntaxes● Stored in triplestores● SPARQL query language
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  Triples/QuadsGraph Subject Property Object http://www.w3.org/ http://www.w3.org/ http://www.w3.org/ People/EM/contact# 1999/02/22-rdf- 2000/10/swap/pim/c me syntax-ns#type ontact#Person http://www.w3.org/ http://www.w3.org/ "Eric Miller" People/EM/contact# 2000/10/swap/pim/c me ontact#fullName http://www.w3.org/ http://www.w3.org/ mailto:em@w3.org People/EM/contact# 2000/10/swap/pim/c me ontact#mailbox http://www.w3.org/ http://www.w3.org/ "Dr." People/EM/contact# 2000/10/swap/pim/c me ontact#personalTit leExample from RDF Primer
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  RDF graph
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  Multiple syntaxes● RDF/XML (the only W3C standard so far)● Plain text ● Turtle (soon W3C standard) ● N-Triples ● Notation3● Namespaces is a shorthand mechanism ● foo: http://example.org/somewhere/ ● ex: http://example.org/somewhere/ ● foo:bar = http://example.org/somewhere/bar ● foo:bar == ex:bar
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  RDF/XML syntax<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"xmlns:contact="http://www.w3.org/2000/10/swap/pim/contact#"> <contact:Person rdf:about="http://www.w3.org/People/EM/contact#me"> <contact:fullName>Eric Miller</contact:fullName> <contact:mailbox rdf:resource="mailto:em@w3.org"/> <contact:personalTitle>Dr.</contact:personalTitle> </contact:Person></rdf:RDF>
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  Turtle syntax@prefix contact:<http://www.w3.org/2000/10/swap/pim/contact#> .<http://www.w3.org/People/EM/contact#me> a contact:Person ; contact:fullName "Eric Miller" ; contact:mailbox <mailto:em@w3.org> ; contact:personalTitle "Dr." .
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  OWL (Web OntologyLanguage)● Based on formal semantics ● Enables inference (reasoning)● Open world assumption ● Unknown is not false but undefined● Builds on RDF Schema ● Class (set of individuals) ● Property – Datatype – Object ● Instance (individual)
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  Ontologies●Established, reusable vocabularies/schemas ● DublinCore: basic metadata ● FOAF: person and contact information ● SIOC: social media descriptions ● GoodRelations: e-commerce
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  SPARQL: RDF querylanguage● RDF graph pattern matching● The only standard NoSQL query language● SPARQL forms ● SPARQL Update forms ● SELECT ● INSERT DATA ● ASK ● DELETE DATA ● DESCRIBE ● INSERT/DELETE ● CONSTRUCT ● LOAD ● CLEAR
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  SPARQL examplePREFIX contact:<http://www.w3.org/2000/10/swap/pim/contact#>SELECT *{ ?person contact:mailbox ?mbox } ?person ?mboxhttp://www.w3.org/People/EM/contact#me mailto:em@w3.org
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  RDF & SPARQLtools● Frameworks ● Apache Jena ● Sesame● Triplestores ● Dydra (cloud) ● Stardog ● Virtuoso ● BigData
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  Linked Data● Linked Data = RDF + REST● Linked Data platform (soon W3C standard) ● Item resources and container resources ● Implement HTTP methods ● Accept and return RDF descriptions● Uniform generic web API● The only global data integration approach
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  Linked Data usage● Open datasources ● DBPedia ● Linked Life Data ● UK Open Data● In companies ● BBC: Semantic Publishing ● IBM: Linked Data Basic Profile 1.0
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  Further reading● RDF Primer● OWL 2 Web Ontology Language Primer● SPARQL by Example● Learning SPARQL● Linked Data: Evolving the Web into a Global Data S
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  Graphity●Generic open-source Linked Data platform ● Independent from domain models and datasources● Architecture ● Model: pure RDF, no object model (above RDF API) – Generated SPARQL queries load RDF from triplestore ● View – XSLT transforms RDF/XML to XHTML ● Controller – JAX-RS web application matches requests, queries & transforms
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  Thanks. Questions?● Martynas Jusevičius● Vilnius/Copenhagen● martynas@graphity.org● @pumba_lt