samad paydar web technology laboratory computer engineering department ferdowsi university of...
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Samad Paydar
Web Technology LaboratoryComputer Engineering Department Ferdowsi University of Mashhad1389/11/20
An Introduction to the Semantic Web
Outline
• Why Semantic Web?• What is Semantic Web?• Semantic Web Main Technologies• Semantic Web Timeline
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Mom
Physician’s Agent
Lucy’s Agent
requiredtreatment
Schedule appointment
Insurance Co.
Provider sites
Rating
in-plan?close-by?Specialist?
Pete’ Agent
Driving schedule
Semantic Web Scenario
The Vision
• The World Wide Web (the syntactic web) is a big and impressive success story, both in terms of – the amount of available information and– the growth rate of human users
• It has entered most areas of our daily life and business.
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The Vision
• This success is based on its simplicity– It’s easy to publish information on the web– It’s easy to access information (but if you know
where they are)
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Why Semantic Web?
• Tasks often require to combine data on the Web:– hotel and travel information may come from different
sites– searches in different digital libraries
• Humans combine these information easily even if– different terminologies are used– the information is incomplete, or buried in images,
videos, …
• But Machines?
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What is the Problem?
Challenge
• Query– What is the name of a person who is a member of
an organization in Iran, and likes a kind of sport?
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Why Semantic Web?
• (Some) data should be available for machines for further processing– Metadata: Data about data
• Data should be possibly combined, merged on a Web scale
• Machines may also need to reason about that data
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What is Semantic Web?
• Tim Berners-Lee:
–“The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation.” 2001
Semantic Web
• “The Semantic Web will bring structure to the meaningful content of Web pages, creating an environment where software agents roaming from page to page can readily carry out sophisticated tasks for users” 2001
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Current Web
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Current Web
• Resources– identified by URI's – untyped
• Links– href, src, ... – limited, non-descriptive
• User– Exciting world - semantics of the resource, however, gleaned from
content
• Machine: – Very little information available - significance of the links only evident
from the context around the anchor.
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Semantic Web
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Semantic Web
• Resources– Globally Identified by URI's – or Locally scoped (Blank) – Extensible – Relational
• Links– Identified by URI's – Extensible – Relational
• User– Even more exciting world, richer user experience
• Machine– More processable information is available (Data Web)
• Computers and people– Work, learn and exchange knowledge effectively
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Semantic Web Technologies
• The Semantic Web extends the Web through the use of standards, markup languages and related processing tools
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Semantic Web Layer Cake
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A Simple Web Page
Markup consists of:
rendering information (e.g., font size and colour)
Hyper-links to related content
Semantic content is accessible to humans but not (easily) to computers…
Challenge
• Query– What is the name of a person who is a member of
an organization in Iran, and likes a kind of sport?
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What information can we see…
Hi!My name is Ali!This is my homepage. I am a student at Ferdowsi
University of Mashhad.I like football.
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The Page Source Code in HTML
<html> <head> <title>Ali's Homepage </title></head><body> <p><b>Hi!</b></p> <p><b>My name is Ali!</b></p> </b> <p>This is my homepage. I am a student at <a
href=“http://um.ac.ir">Ferdowsi University of Mashhad</a>.</p> <p>I like football.</p>
</body></html>
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What information can a machine see…
<html> <head> <title>…………………..</title></head><body> <p><b>………</b></p> <p><b>....................</b></p> </b> <p>…………………………………………..……<a
href=“………………”>…………………..</a>.</p> <p>............................</p>
</body></html>
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XML
• XML allows users to add arbitrary structure to their documents but says nothing about what the structures mean
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Solution: XML “meaningful” tags
………………………….
<student>………………….</student><university>……………………..<university>…………………………………………………………………………………………………….
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But What if?
………………………….
<boy>………………….</boy><college>……………………..<college>…………………………………………………………………………………………………….
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RDF
• Resource Description Framework– A data modelo Meaning encoded in sets of ‘triples’: entities have
properties which have valueso Each triple: subject-predicate-objecto Entities, properties and values all have distinct URIs
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RDF
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AliFerdowsi
University of Mashhad
studentOF
http://um.ac.ir
hasHomePage
RDF
<rdf:Description about="some.uri/person/ali"><studentOf resource="some.uri/Ferdowsi_University_of_Mashhad"/>
</Description>
<Description about="Ferdowsi_University_of_Mashhad"> <hasHomePage>http://um.ac.ir</hasHomePage></rdf:Description>
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Challenge
• Query– What is the name of a person who is a member of
an organization in Iran, and likes a kind of sport?
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But…
• What is the relation between – a Student and a Person?– Football and Sport?– University and College?– University and Website?
• Ontology is the solution
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Ontology
• Ontologies provide semantic• Main elements of an ontology:
– Concepts– Relationships
• Hierarchical• Logical
– Properties– Instances (individuals)
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Challenge
• Query– What is the name of a person who is a member of
an organization in Iran, and likes a kind of sport?
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Ontology
• To answer the query it is required to tell the machine that– There is a class of objects named ‘Student’– There is a class of objects named ‘Person’– Each Student is a Person– Each Person has a Name– There is a class of objects named ‘Sport Type’– Football is a kind of Sport– There is an instance of a Student that its Name is “Ali”– ….
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Ontology
• Ontology Languages– OWL– RDFS (RDF Schema)– SHOE– DAML+OIL
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Scientific American, May 2001
• Realising the complete “vision” is too hard for now (probably)
• But we can make a start by adding semantic annotation to web resources
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Don’t Forget!
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1895 2006
Semantic Web Layer Cake
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Semantic Web: Now
• Numerous web technologies, languages, formats, and standards which provide the inferastructure– URI, XML, XML Schema, RDF, RDFS, OWL, SPARQL,
SerQL, HTTP, Microformats, RDFa,
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Semantic Web: Now
• A large body of research and activity is related to ontologies, since they play a main role– Ontology engineering issues and tools
• ontology development, ontology selection, ontology matching, ontology evaluation, ontology partitioning,….
– Numerous Ontologies are developed in different domains, e.g. FOAF, DOAP, SIOC, SKOS, …
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Semantic Web: Now
• Semantic Web technologies are used as an enabler in different areas to develop small semantic web applications– Ontology-based …..– Ontology-enabled …– Semantic-Web-Enabled …– Semantic ….
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Semantic Web Application Areas
• Content Discovery• Content Management• Customization and Adaptation• Data Integration• Domain Modeling• Search and Information Retrieval• Social Networks • Automating Tasks• Knowledge Management
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Semantic Web: Now
• Semantic Web Search Engines– Swoogle, SWSE, Watson, Sindice, Falcons, Yahoo!
Microsearch, ….
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Web Evolution Timeline
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Linked Data
– If we see Semantic Web as a long term goal then Linked Data is a major step towards it’s large scale and full-featured realization
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Thanks!!
Any Question?
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