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S emantic Web

S emantic Web. By Ahmet Can Babao ğ lu Abdurrahman Be ş inci. Semantic Web Example. Suppose you want to buy a Star wars DVD having such properties; wide-screen ( not full-screen ) the extra disc of bonus materials lowest available price not paying too much for shipping and handling

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S emantic Web

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  1. Semantic Web By Ahmet Can Babaoğlu Abdurrahman Beşinci

  2. Semantic Web Example • Suppose you want to buy a Star wars DVD having such properties; • wide-screen ( not full-screen ) • the extra disc of bonus materials • lowest available price • not paying too much for shipping and handling • not waiting too long for delivery. What would you do? • The best thing you can do is to search for web pages and look for a suitable item. • However, using semantic web, agents can return the suitable results to you…

  3. Other Examples • An agent lists the prices of flat screen HDTVs with properties; • larger than 40 inches with 1080p resolution • at shops in the nearest town • open until 8pm on Tuesday evenings • Find and buy a airline ticket if there is a route from Istanbul to London this evening with price lower than $150

  4. Invented by Tim Berners-Lee (1998 ) • Inventor of WWW, URIs, HTTP, and HTML • The director of the World Wide Web Consortium ( www.w3.org ) • Senior researcher at the MIT Computer Science and Artificial Intelligence Laboratory

  5. What is semantic web? A Web thatincludes • documents, orportions of documents, • describingexplicitrelationshipsbetweenthingsand • containingsemanticinformationintendedfor • automatedprocessingbyourmachines. TBL’s words; Now web is a huge book, with semantic web, it will be a huge database. A technology helps machines `understand`; • The Beatles was a popular bandfrom Liverpool. • John Lennonwas a member of the Beatles.

  6. New Features • Machine process-able • Data integration • Meaningful web pages • Making deductions • SW is not AI and AI is not SW SW should be a great playground for AI

  7. Goals • Web of data - provides common data representation framework to facilitate integrating multiple sources to draw new conclusions • Increase the utility of information by connecting it to its definitions and to its context • More efficient information access and analysis

  8. Applications • Agents searching Web and retrieving valuable information to the end user. • Web services publishing their information • Programs running to merge data of different web services and create new results from them.

  9. Current Web • User: Exciting world - semantics of theresource, understood from content • Machine: Very little information available , only links

  10. Semantic Web • User: Even more exciting world, richer user experience • Machine: More processable information is available (Data Web)

  11. SW Architecture • Metadata layer ( Resource and property ) RDF ( Resource Description Framework ) • Schema layer (Hierarchical description of concepts ) RDF-S ( RDF Schema ) • Logical layer ( class relations, uses logic ) OWL ( Web Ontology Language )

  12. SW Architecture ( contd. )

  13. XML & RDF • XML: uses tags to describe data • RDF: • provides a framework to describe resources. • uses triples written as XML tags to express this information as a graph.

  14. XML & RDF (contd. ) Q: There is a father relation between Anakin and Luke ok but, who or what is Anakin and Luke ? What does father mean anyway? A: RDF uses uniform resource identifiers (URIs) to direct the computer to a document or object that represents the resource.

  15. RDF-S & OWL • Computers don't have the kind of vocabulary that people do. So the computer has to have documents that describe all the words and logic to make the necessary connections. • RDF-S: adds classes, subclasses and properties to resources, creating a basic language framework • OWL: formalizes ontology, describes relationships between classes and uses logic to make deductions. It can also construct new classes based on existing information.

  16. RDF Example <http://aaronsw.com/> <http://love.example.org/terms/reallyLikes> <http://www.w3.org/People/Berners-Lee/Weaving/> . Explanation; The first URI is the subject. the subject is me. The second URI is the predicate. It is "reallyLikes." The third URI is the object. The object is Tim Berners-Lee's book "Weaving the Web." So the RDF statement above says that I really like "Weaving the Web.“ RDF code; <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:love="http://love.example.org/terms/" > <rdf:Description rdf:about="http://aaronsw.com/"> <love:reallyLikes rdf:resource="http://www.w3.org/People/Berners-Lee/Weaving/" /> </rdf:Description> </rdf:RDF>

  17. RDF-S Example • To declare a vocabulary or properties • specify the (multiple)-inheritance links between the types of classes (subClassOf or subProperty); • machines determine the meanings of resources based on properties and classes.

  18. RDF-S Example ( contd. ) <rdf:RDF xml:base="http://www.inria.fr/2007/04/17/humans.rdfs" xmlns:rdf ="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns="http://www.w3.org/2000/01/rdf-schema#"> <Class rdf:ID="Man"> <subClassOf rdf:resource="#Person"/> <subClassOf rdf:resource="#Male"/> <label xml:lang="en">man</label> <comment xml:lang="en">an adult male person</comment> </Class> <rdf:Property rdf:ID="hasMother"> <subPropertyOf rdf:resource="#hasParent"/> <range rdf:resource="#Female"/> <domain rdf:resource="#Human"/> <label xml:lang="en">has for mother</label> <comment xml:lang="en">to have for parent a female.</comment> </rdf:Property> </rdf:RDF> We declare a class #Man, sub class of #Person and #Male, and a property #hasMother having sub property of #hasParent, and that is used between instances of the class #Human and instances of the class #Female.

  19. OWL Example making logical deductions. For instance, given the ontology above, a Semantic Web agent could infer that since "Goose" is a type of "DarkMeatFowl," and "DarkMeatFowl" is a subset of the class "Fowl," which is a subset of the class "EdibleThing," then "Goose" is an "EdibleThing."

  20. OWL Example <owl:SymmetricProperty rdf:ID="sibling"> <rdfs:domain rdf:resource="#Animal" /> <rdfs:range rdf:resource="#Animal" /> </owl:SymmetricProperty> A property is symmetric.

  21. Data merging

  22. Advantages • Precise search results • Time efficient for human • Easy to publish information • More human like thinking ( one step closer ) • Data integration • Machine process-able

  23. Problems of SW • The learning curve. RDF was developed by people with academic background in logic and artificial intelligence. For traditional developers it is not very easy to understand. • All the web pages’ content must be changed which is a long process. • Unrealized idea; "This simple idea, however, remains largely unrealized." • Two formats for one piece of data: one for human viewing and one for machines • concerns regarding censorship and privacy (for governments to control the viewing and creation of online information )

  24. Future Directions • Semantic Web infrastructure - stimulate the network effect of data • Data Access • Best Practices for vocabulary / ontology development • Development of ontology registries for Open vocabularies

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