Overview of Semantic Tools Semantic Technology Boot Camp Day 3.
Semantic Technology: A Basic Introduction
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Transcript of Semantic Technology: A Basic Introduction
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Dr. Lowell VizenorOntology and Semantic Technology Practice Lead
Alion Science and Technology
Semantic Technology: A Basic Introduction
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Overview
1. The underlying idea of the Semantic Web and Linked Data
2. Semantic Web standards: RDF/S, SPARQL 1.1, and OWL 2
3. Basic tools and methods (including TopBraid and Protégé, Reasoners)
4. An example: Universal Core Semantic Layer (UCore SL)
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Web 2.0 and Beyond• Web 2.0
– O'Reilly Media Web 2.0 Conference (2004)– Characteristics
• Web as platform• Democratizing the Web• Distributed data
– Examples: Social-networking sites (Facebook, LinkedIn), blogs (Blogger), wikis (Wikipedia), video-sharing sites (YouTube), hosted services, web applications, mashups and folksonomies (Digg)
• … and Beyond– Web 3.0 = Semantic Web?– Tim Berners-Lee, James Hendler and Ora Lassila. The Semantic Web : A new form of Web
content that is meaningful to computers will unleash a revolution of new possibilities, Scientific American, May 17, 2001
– Key idea: Metadata added to Web pages can make the existing World Wide Web machine readable (or the Web as a distributed database).
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Semantic Web - Example
• Dinner and a Movie – Assume that you and your date want to have dinner at an Italian
restaurant and then go and see a movie that your friends have recommended on a social networking site, that is within walking distance of the restaurant, and starts two hours after your dinner reservation.
– Current approach: Search multiple sites and manually cross-reference the information and make a decision.
– Semantic Web vision: • a computerized agent performs search based on user inputs and
metadata• recommends best options, and• makes reservations, purchases movie tickets for you, and sends out
calendar invite.
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Applying Semantic Web Architecture to the Enterprise
Semantic Web Stack
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RESOURCE DESCRIPTION FRAMEWORK (RDF)
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RDF Data Model
Subject Predicate Object
Statement 1 p1 type Person
Statement 2 p1 name John Smith
Statement 3 p1 mbox [email protected]
• An RDF graph is a set of RDF triples– Subject/Predicate/Object– Triples are statements (i.e. they are true or false)– The smallest graph is a single triple
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RDF Graph Data Model
Subject Predicate Object
Statement 1 p1 type Person
Statement 2 p1 name John Smith
Statement 3 p1 mbox [email protected]
ex:p1
foaf:Person
“John Smith”
rdf:typefoaf:name
foaf:mbox
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Anatomy of a URI• Uniform Resource Identifier (URI)
– Definition• A Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical
resource.
– Example URI<http://xmlns.com/foaf/0.1/Person>
– Every URI has a namespace<http://xmlns.com/foaf/0.1/Person>
– Every URI has a local name<http://xmlns.com/foaf/0.1/Person>
– Qname or aliasfoaf:Person@prefix foaf: <http://xmlns.com/foaf/0.1/>
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“Cool URIs don’t change” – Tim Berners-Lee
@prefix foaf: <http://xmlns.com/foaf/0.1/>@prefix ex: <http://www.example.com/example#>
ex:p1
foaf:Person
“John Smith”
rdf:typefoaf:name
foaf:mbox
Anatomy of a URI
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URI Resources and Labels
elem:Mercury
myth:Mercury
“Mercury”“Hermes”
skos:prefLabel
skos:prefLabel
skos:altLabel
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Merging Graphs
ex:p1 foaf:Person
“male”^^xsd:string
“45”^^xsd:int
foaf:gender
foaf:age
ex:p1
foaf:Person
“John Smith”^^xsd:string
<mailto:[email protected]>
rdf:typefoaf:name
foaf:mbox
rdf:type
Dataset 1
Dataset 2
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Merging Graphs
ex:p1“male”^^xsd:string
“45”^^xsd:int
rdf:type
foaf:gender
foaf:age
ex:p1
foaf:Person
“John Smith”^^xsd:string
<mailto:[email protected]>
rdf:type
foaf:name
foaf:mbox
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Linked Open Data
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Linked Data Principles
• Use URIs as names for things
• Use HTTP URIs so that people can look up those names.
• When someone looks up a URI, provide useful information, using the standards (RDF, SPARQL)
• Include links to other URIs. so that they can discover more things.
Tim Berners-Leehttp://www.w3.org/DesignIssues/LinkedData.html
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SPARQL 1.1SPARQL Query Language for RDF
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Select all the persons
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Select every one named “Alice”
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Who does Alice know?
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Who is Alice connected to via foaf:knows?
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Who does Alice not know?
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Alice knows everyone who Ted knows
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SPARQL FEDERATION DEMO