Linked Data

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My academic seminar presentation on Linked Data

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Linked Data

  1. 1. Web == One huge DB A seminar on Linked Data and Semantic Web
  2. 2. The Web of Linked Documents
  3. 3. Issues of Linked Documents <ul><li>Loosely structured Data
  4. 4. Unstructured hyperlinks
  5. 5. Disconnected Data </li></ul>
  6. 6. What is Semantic Web? “ The first step is putting data on the Web in a form that machines can naturally understand, or converting it to that form. This creates what I call a Semantic Web – a web of data that can be processed directly or indirectly by machines.” ~ Tom Heath
  7. 7. The Web of Linked Data
  8. 8. The Semantic Web <ul><li>This converts the whole web into a single database.
  9. 9. Designed for machines and humans.
  10. 10. Links between things-things and things-and its description.
  11. 11. Encourages reuse, reduces redundancy
  12. 12. Enables to add more value to data over the network. </li></ul>
  13. 13. Linked Data Technology Stack <ul><li>URIs
  14. 14. HTTP
  15. 15. RDF (Resource Description Framework)
  16. 16. RDFS/OWL </li></ul>
  17. 17. URIs – Not Just for Web Pages <ul><li>“A Uniform Resource Identifier (URI) provides a simple and extensible means for identifying a resource.” -- RFC 3986
  18. 18. Examples </li><ul><li>http://dbpedia.org/resource/Tim_Berners-Lee
  19. 19. http://dbpedia.org/resource/Model_Engieering_College
  20. 20. http://sws.geonames.org/4671654/ </li></ul></ul>
  21. 21. HTTP <ul><li>Data access mechanism
  22. 22. Using http:// URIs to identify things allows people to look these things up </li></ul>
  23. 23. RDF: Resource Description Framework <ul><li>Data format for describing things and their interrelations.
  24. 24. Descibes relations based on triples; subject-predicate-object </li></ul>
  25. 25. The RDF Data Model <ul>subject -> predicate -> object Tom -> worksFor -> Talis Talis -> basedIn -> Birmingham <uri> -> <uri> -> <uri> eg: <http://dbpedia.org/resource/Talis_Group> <http://xmlns.com/foaf/0.1/based_near> <http://sws.geonames.org/3333125/> </ul>
  26. 26. Data Merging with RDF <ul><li>Consider a profile of Richard </li></ul>
  27. 27. Data Merging with RDF <ul>This can be naturally merged </ul>
  28. 28. Data Merging with RDF <ul><li>This is linked Data </li></ul>
  29. 29. Data discovery in RDF
  30. 30. Advantages of RDF <ul><li>Information in different sources merge naturally
  31. 31. Clients can look up every URI in and RDF graph over the Web to get addictional info.
  32. 32. Easy description of relations with the help of RDFS </li></ul>
  33. 33. Linked Data principles <ul><li>Use HTTP URIs
  34. 34. Provide useful information in RDF
  35. 35. Include RDF links to other URIs </li></ul>
  36. 36. Why publish Linked Data? <ul><li>Ease of discovery
  37. 37. Ease of consumption </li><ul><li>standards-based data sharing </li></ul><li>Reduced redundancy
  38. 38. Added value </li><ul><li>build ecosystems around your data/content </li></ul></ul>
  39. 39. The Linking Open Data Project
  40. 40. The Linking Open Data Project <ul><li>Community project with W3C support
  41. 41. Take existing open data sets
  42. 42. Make them available on the Web in RDF
  43. 43. Interlink them with other data sets
  44. 44. Began early 2007 </li></ul>
  45. 45. LOD Cloud as on November 2007
  46. 46. LOD Cloud as on March 2008
  47. 47. LOD Cloud as on March 2009
  48. 48. The latest LOD cloud as on July 2009
  49. 49. Setting RDF links <ul><li>RDF links enable LD browsers and crawlers to discover additional data
  50. 50. The application domain determine the RDF properties used in predicate section. </li><ul><li>eg: for describing people : foaf:knows, foaf:based_near
  51. 51. for showing another same data source: owl:sameAs </li></ul><li>We can set the RDF links manually and generate links automatically using algorithms. </li></ul>
  52. 52. Generating RDF links manually <ul><li>Identify the datasets you want to link to.
  53. 53. Search for the right URIs to link to using search interfaces if provided. Or using LD browsers
  54. 54. Use services like Uriqr to search for existing URIs and choose the most popular one suiting your need. </li></ul>
  55. 55. Auto generating RDF links <ul><li>Used on Large datasets
  56. 56. Two major methods </li><ul><li>Pattern Based algorithm </li><ul><li>Searches the URIs on various data sets for similar patterns and link generate the RDF links </li></ul><li>Property based algorithms </li><ul><li>Searches additional informations of the resource at the resource end points rather than the URIs alone. </li><ul><li>Eg: interlinking Dbpedia and Geonames. </li></ul></ul></ul></ul>
  57. 57. Now how to put it on Linked Data <ul><li>Serve as static files </li><ul><li>Simplest way is to produce static RDF files and upload them to your webserver. </li><ul><li>When creating FOAF profiles, and RDF vocabularies
  58. 58. RDF is generated by some other software. </li></ul></ul><li>Serving RDB on </li><ul><li>The conventional DB is untouched
  59. 59. A mapping is done to produce the RDF files.
  60. 60. Tools like D2R server and OpenLink Virtuoso is used. </li></ul></ul>
  61. 61. RDB to Linked Data
  62. 62. SPARQL <ul><li>S PARQL P rotocol a nd R DF Q uery L anguage
  63. 63. Retrieves data from RDF
  64. 64. Similar to SQL syntax </li><ul><li>Eg: </li></ul></ul><ul><ul><li>PREFIX foaf: < http://xmlns.org/foaf/0.1/ > </li></ul></ul>SELECT ?acquaintance FROM < http://w3.org/People/Berners-Lee/card > WHERE { < http://w3.org/People/Berners-Lee/card#i > foaf:knows ?acquaintance . FILTER isURI(?acquaintance) }
  65. 65. Linked Data Applications
  66. 66. Linked Data Applications <ul><li>Browsers </li><ul><li>Marbles </li></ul><li>Search engines </li><ul><li>Falcons </li></ul><li>Mashups </li><ul><li>Dbpedia Mobile
  67. 67. Talis Aspire
  68. 68. DERI pipes </li></ul></ul>
  69. 69. Challanges <ul><li>User Interface
  70. 70. Link Maintenance
  71. 71. Licensing
  72. 72. Trust, Quality, Relevance </li></ul>
  73. 73. Conclusions <ul><li>Linked Data will enable revolution on how data will be used
  74. 74. Machines will finally be able to search!!
  75. 75. Researchers can have a wide range of related data to dig into. </li></ul>
  76. 76. “ RAW DATA NOW! ” ~Tim Berners
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