![Introduction
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 co-
operation.
[Tim Berners-Lee , 2001]
3](https://image.slidesharecdn.com/semanticweb-120916124148-phpapp02/85/Semantic-web-3-320.jpg)
Semantic web
- 1. Semantic web Tapas Kumar Mishra 11CS60R32 1
- 2. Agenda Introduction What is semantic web Issues with traditional web search The Technology Stack Architecture of semantic web Meta Data Main Tasks Knowledge Representation ∙ XML ∙ RDF Ontology ∙ Taxonomy ∙ Inference Rules Conclusion And references 2
- 3. Introduction 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 co- operation. [Tim Berners-Lee , 2001] 3
- 4. Introduction contd… • Traditional search Displays the pages that contain the words without interpreting the meaning of those words. 4
- 5. Introduction contd… • Semantic Search retrieves the meaning from the bag of words 5
- 6. Semantic Web Stack 6
- 8. Metadata • The first form of semantic data on the Web was metadata : information about information • Basically include: 1. Means of creation of the data 2. Purpose of the data 3. Time and date of creation 4. Creator or author of data 5. Placement on a computer network where the data was created 6. Standards used 8
- 9. Metadata Contd.. Example : • a meta element specifies name and associated content attributes describing aspects of the HTML page. <meta name="keywords"content="wikipedia,encyclopedia"> • default charset for plain text is simply set with meta: <meta http-equiv="Content-Type" content="text/html charset=UTF-8" > 9
- 10. Semantic Web main tasks • Knowledge Representation: • Metadata annotation • Description of resources using standard languages • Search: • Retrieve relevant information according to user‟s query / interest / intention • Use metadata (and possibly content) in a “smart” way (i.e. “reasoning” about the meaning of annotations) 10
- 11. Knowledge Representation 11
- 12. URI • string of characters used to identify a name or a resource on the Internet • Categorized into 2 types • URL Uniform Resource Locator • URN Uniform Resource Name • URN defines an item's identity, while the URL provides a method for finding it • Example: • URN ----> ISBN of books, ISBN 0486275574 cites, unambiguously, a specific edition of Shakespeare's play Romeo and Juliet. 12
- 13. XML • User definable and domain specific markup <course date=“...”> course <title>...</title> <teacher>... title students <name>...</name> <http>...</http> </teacher> = teacher <students>...</students> name http </course> • XML provides an elemental syntax for content structure within documents • But associates no semantics with the meaning of the content contained within. 13
- 14. RDF(Resource Description Framework) • corner stone of the Semantic Web technology stack • 1999, first publication • directed and labeled graphs as data model • everything is univocally identifiable with a Uniform Resource Identifier(URI) • a web page, a person, a book, an intangible thing 14
- 15. RDF CONTD… A statement is a triple Subject –predicate –object Subject: a resource Predicate: a verb / property / relationship Object: a resource, or a literal string Relationships between things could be expressed with a directed, labeled graph where • nodes could be resources or XMLSchema-typed values and • relationships are identified also by URIs 15
- 16. RDF CONTD… Author = D.West Diagram: hasAuthor URI D.West Simple RDF assertion triple : triple (hasAuthor, URI, D.West) RDF in XML syntax: <RDF xmlns=“http://www.w3.org/TR/ … ” > <Description about=“http://www. w3.org/semweb/intro”> <Author>D.West</Author> </Description> </RDF> 16
- 17. RDF(S): RDF Schema • Defines vocabulary for RDF • Organizes this basic vocabulary terms and the relations between those terms -Class, subClassOf, type -Property, subPropertyOf -domain, range Person subClassOf subClassOf Student range domain teaches Teacher type type teaches Prof.X Student Y 17
- 18. RDF CONTD… • triples of RDF form webs of information about related things. • the URIs ensure that concepts are not just words in a document but are tied to a unique definition that everyone can find on the Web. Example: a database of info of people , including their addresses. RDF can specify that "(field 5 in database A) (is a field of type)(zip code),“ Query: Find people living in city with zipcode x 18
- 19. RDF CONTD… • Problem with RDF: o Synonym problem: • two databases may use different identifiers for what is in fact the same concept, such as zip code. A program that wants to compare or combine information across the two databases has to know that these two terms are being used to mean the same thing. 19
- 20. Ontology • Problems with RDF • two databases may use different identifiers for what is in fact the same concept, such as zip code • Solution is Ontology…. An ontology is an explicit description of a domain • concepts • properties and attributes of concepts • constraints on properties and attributes • individuals (often, but not always) Web ontology consists of • Taxonomy • Inference Rules 20
- 21. Ontology Contd… ontology that describes the Webify Solutions 21 organization
- 22. Taxonomy • Defines classes of objects and relations among them 22
- 23. Taxonomy Contd… HOW Taxonomy helps: • classes, subclasses and relations among entities are a very powerful tool for Web use • city codes must be of type city and cities generally have Web sites, we can discuss the Web site associated with a city code even if no database links a city code directly to a Web site. city Has a website contains citycode 23
- 24. Inference Rules • Allows us to infer conclusions based on rules and facts available in the knowledge base • Example: • An ontology may express the rule "If a city code is associated with a state code, and an address uses that city code, then that address has the associated state code." • A program could then readily deduce, for instance, that a IIT KGP address, being in Kharagpur, must be in West Bengal, which is in the India, and therefore should be formatted to indian standards. 24
- 25. Inference Rules contd.. • this solve RDF’s synonym problem. • Example: • an ontology that defines addresses as containing a zip code and another ontology uses postal code. • The program could then use a service that takes • a list of postal addresses (defined in the first ontology) and • converts it into a list of physical addresses (the second ontology) by recognizing and removing post office boxes and other unsuitable addresses. 25
- 26. PRO’s of Semantic web • Accuracy of web search • Tackle complicated questions • Inpage answer to query 26
- 27. CONCLUSIONS AND FUTUREWORK • Implementation of encryption layer • Standard for retrieval • Standard for metadata 27
- 28. References 1. Berners-Lee, Tim; James Hendler and Ora Lassila (May 17, 2001). "The Semantic Web". Scientific American Magazine 2. www.en.wikipedia.org/wiki/Semantic_Web 3. Tim Berners-Lee, with Mark Fischetti. Harper San Francisco, 1999.”Weaving the Web” 4. http://www.w3.org/2001/sw/ 5. www.SemanticWeb.org/ 6. James Farrugia,University of Maine, Orono, ME. ” Model-theoretic semantics for the web”. ACM New York, NY, USA ©2003 28
- 29. Thank you 29