Semantic Web

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Semantic Web

• The Web with Semantics

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What is the Semantic Web?

• Knowledge Representation on the (decentralized)
  web.
• Definitions from Google

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Key Features of the Semantic Web

• Content meaningful to computers
• XML, RDF
• Defining the world in objects (xml)
• URIs, not words, for concepts and associations.
• Decentralized and open
• anyone can publish data about anything

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Decentralized and Open

• Anyone can define attributes of anything.
• Berners Lee says Web doesnt discriminate
  between paper napkins and well-thought out
  refereed articles. Is this true?

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The Old Web
dynamic page
static page
Servlet
Server
Database
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The Web with Semantics
Database
Servlet
rdf
xml
Service
Server
Database
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The Web with Semantics
Database
Servlet
Objects, Associations, Reasoning Rules
rdf
xml
Service
Server
Database
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3-Layer DB Approach on the Web
Servlet
Software Agent
rdf
xml
Service
Server
Database
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Sample Questions for the Semantic Web

• Find the Ms. Cook I met at a trade conference
  last year.
• Get me a list of all academic publications
  concerning metasearch systems

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Traditional Knowledge Representation

• Closed Systems that cant talk to each other
• Narrow, Idiosyncratic

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Knowledge Representation on Web

• RDF is the glue
• Formerly closed systems can publish RDF
• Can also publish RDF translators vis-à-vis
  similar systems
• Theres a lot of low hanging fruit.

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XML

• XML clause is
• propertystring lt-gt valuestring
• ltlastnamegt wolber lt/lastnamegt
• An object is a hierarchical set of clauses
• ltpersongt
• ltlastnamegt wolber lt/lastnamegt
• ltfirstnamegt david lt/firstnamegt
• lt/persongt

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RDF adds universality and subjects to each clause

• RDF Clause is a triple
• subjecturi propertyuri valueuri
• ltcs.usfca.edu/wolbergt
• ltfoaflastgt
• ltwolbergt
• ltcs.usfca.edu/wolbergt
• ltfoaffirstgt
• ltwolbergt

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XML vs. RDF
ltpersongt ltlastnamegt wolber lt/lastnamegt ltfirst
namegt david lt/firstnamegt lt/persongt
ltcs.usfca.edu/wolbergt ltfoaflastgt ltwolbergt ltcs.us
fca.edu/wolbergt ltfoaffirstgt ltwolbergt
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Property is a URI

• Can go there and see precise definition
• Allows standards to build up
• e.g., dublin core, foaf
• People can write equivalence equations with RDF.

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In-Class Research Assignment

• There is foaf, dublin core, rdf
• Lets compile a catgorized listing of all rdf
  schemas, including those.
• Films, Books, relationships between people
• Lets build a wiki page on it.