Slides from the presentation I gave in my Information Retrieval class at NorthEastern in June 2009. The class was taught by Javed Aslam.

1. Intro to the
Semantic Web
Peter Snyder
snyderp@gmail.com
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2. Outline
• What Is the Semantic Web?
• What Problem is it Trying to Solve?
• How does it Solve the problem?
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3. What is the SW?
• Effort to
1. make data on the web machine friendly
2. using existing open technologies
3. in order to aid information retrieval
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4. What is the SW? ....
• Made up of
- XML
- XML Schema
- RDF
- RDF Schema / OWL
- SPARQL
4

5. Outline
• What Is the Semantic Web?
• What Problem is it Trying to Solve?
• How does it Solve the problem?
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6. What is the Problem?
• Web is human oriented
• All nonsense to machines
• Humans waste time
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7. Example
http://www.peteresnyder.com/fake
<div>
<h1>My Homepage</h1>
<p>Hi, I'm Peter E. Snyder.
<p>I live in Cambridge.
<p>I like the band The Fall!
<p>I love professional wrestling!
</div>
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8. Outline
• What is the semantic web?
• What problem is it trying to solve?
• How does it solve the problem?
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9. Solution
• Basic Track (Microformats)
• W3C Recommendation (Alphabet Soup)
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10. Microformats
<div class="vcard">
<p>
<a class="url" href="http://www.peteresnyder.com">
http://www.peteresnyder.com
</a>
</p>
<p>
<strong>Name:</strong>
<span class="fn">Peter Snyder</span>
</p>
<p>
<strong>City:</strong>
<span class="locality">Cambridge</span>
</p>
</div>
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11. W3C Recommends...
• XML
• XML Schema
• RDF
• RDF Schema / OWL
• SPARQL
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12. XML
<?xml version="1.0"?>
<person>
<name>Peter Snyder</name>
<website>http://www.peteresnyder.com<website>
<city>Cambridge</city>
<interests>
<interest>The Fall</interest>
<interest>Professional Wrestling</interest>
</interests>
</person>
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13. XML Schema
XML Schema
<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="person">
<xs:complexType>
<xs:sequence>
<xs:element name="website" type="xs:string"/>
<?xml version="1.0"?>
<xs:element name="name"xmlns:pes=”http://www.peteresnyder.com/fake_schema”>
<person type="xs:string"/>
<xs:element name="city" type="xs:string"/>
<pes:name>Peter Snyder</pes:name>
...
<pes:website>http://www.peteresnyder.com<pes:website>
<pes:city>Cambridge</pes:city>
<pes:interests>
<pes:interest>The Fall</pes:interest>
<pes:interest>Professional Wrestling</pes:interest>
</pes:interests>
</pes:person>
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XML Document

14. RDF
• Resource Description Framework
• Description of relationships (taxonomy)
• Triplets
- subject: thing being described (URI)
- predicate: what the relationship is
- object: the object being related to
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15. RDF Cont.
<urn:name:peteresnyder> <name> "Peter Snyder" .
<urn:name:peteresnyder> <city> "Cambridge" .
<urn:name:peteresnyder> <likes> "The Fall" .
<?xml version="1.0"?>
<rdf:RDF>
<Human rdf:about="urn:name:peteresnyder">
<name>Peter E Snyder</name>
<city>Cambridge</city>
<likes>The Fall</likes>
...
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16. RDF Schema / OWL
• Defines a standard way that things interact
(ontology)
• Common Examples
- Dublin Core: Publishing
- Friend of a Friend (FOAF): People
- OWL is RDFS+
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17. RDFS / OWL Cont.
FOAF RDF Schema
<?xml version="1.0"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:foaf="http://xmlns.com/foaf/0.1/">
<foaf:Person rdf:about="urn:name:peteresnyder">
<foaf:homepage rdf:resource="http://www.peteresnyder.com"/>
<foaf:givenname>Peter</foaf:givenname>
<foaf:family_name>Snyder</foaf:family_name>
<foaf:interest>The Fall</foaf:interest>
....
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18. SPARQL
• SPARQL Protocol and RDF Query
Language
• SQL like language for getting data out of
RDF connections / graphs
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19. SPARQL Cont.
<foaf:Person rdf:about="urn:name:markesmith">
<foaf:Person rdf:about="urn:name:tinafey">
<foaf:homepage rdf:resource="http://www.peteresnyder.com"/>
<foaf:Person rdf:about="urn:name:peteresnyder">
<foaf:homepage rdf:resource="http://www.peteresnyder.com"/>
<foaf:givenname>Peter</foaf:givenname>
<foaf:homepage rdf:resource="http://www.peteresnyder.com"/>
<foaf:givenname>Peter</foaf:givenname>
<foaf:family_name>Snyder</foaf:family_name>
<foaf:givenname>Peter</foaf:givenname>
<foaf:family_name>Snyder</foaf:family_name>
<foaf:interest>The Fall</foaf:interest>
<foaf:family_name>Snyder</foaf:family_name>
<foaf:interest>The Fall</foaf:interest>
...
<foaf:interest>The Fall</foaf:interest>
...
...
+
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?givenname ?family_name
WHERE { ?x foaf:interest "The Fall"}
=
?givenname ?family_name
“Peter” “Snyder”
“Mark” “Smith”
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20. Conclusion
Current Web Semantic Web
<div> <?xml version="1.0"?>
<h1>My Homepage</h1> <rdf:RDF xmlns:foaf="http://xmlns.com/foaf/0.1/">
<p>Hi, I'm Peter E. Snyder. <foaf:Person rdf:about="urn:name:peteresnyder">
<foaf:homepage rdf:resource="http://
<p>I live in Cambridge.
www.peteresnyder.com"/>
<p>I like the band The Fall!
<foaf:givenname>Peter</foaf:givenname>
<p>I love professional
<foaf:family_name>Snyder</foaf:family_name>
wrestling!
<foaf:interest>The Fall</foaf:interest>
</div>
...
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