2011 05-02 linked data intro
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  • 1. Aristotle University, Department of Mathematics
    Master in Web Science
    supported by Municipality of Veria
    From Gore’s information highways to Obama’s Linked data
    Μιχάλης Βαφόπουλος
  • 2. From Al Gore
    (internet highways)
    to Barack Obama
    (linked data)
    2
  • 3. The Web of Documents
    • Analogy:a global file system
    • 4. Designed for: human consumption
    • 5. Primary objects: documents
    • 6. Links between: documents(or sub-parts of)
    • 7. Degree of structure in objects: fairly low
    • 8. Semantics of content and links: implicit (humans)
    (Tom Heath)
    The web = the internet
    + links + documents
    3
  • 9. The Web of Documents
    • Simple, big and unstructured
    • 10. Organized in Silos
    But humans are interested in:
    • Things, no documents and
    • 11. these Thingsmight be
    in documents or elsewhere
    • Humans: Limited capacity
    to extract meaning...
    4
  • 12. Limited SEARCH capacity
    Search for: Football Players who went to the University of Texas at Austin, played for the Dallas Cowboys as Cornerback
    (Juan F. Sequeda)
    5
  • 13. Google, Bing, yahoo! irrelevant
    6
  • 14. Wikipedia through LD: relevant
    7
  • 15. The Web of Data
    • Analogy:a global filesystem----> globaldatabase
    • 16. Designed for: human consumption ->machines first, humans later
    • 17. Primary objects: documents --> things (or descriptions of things)
    • 18. Links between: documents--> things
    • 19. Degree of structure in objects: fairly low ---> high
    • 20. Semantics of content and links: implicit --> explicit
    (Tom Heath)
    8
  • 21. The Modigliani Test
    Show me all the locations of all the original paintings of Modigliani
    Daniel Koller (@dakoller) showed that you can find this with a SPARQL query on DBpedia
    Thanks Richard MacManus - ReadWriteWeb
  • 22.
  • 23. Results of the Modigliani Test
    Atanas Kiryakov from Ontotext
    Used LDSR – Linked Data Semantic Repository
    Dbpedia
    Freebase
    Geonames
    UMBEL
    Wordnet
    Published April 26, 2010:
    http://www.readwriteweb.com/archives/the_modigliani_test_for_linked_data.php
  • 24.
  • 25. The Web of Data: why?
    – encourages reuse
    – reduces redundancy
    – maximises its (real and potential) inter-connectedness
    – enables network effects to add value to data
    13
  • 26. The Web of Data: how?
    – current state on the Web
    (see EXHIBIT)
    Computers can’t consume data because:
    • Different formats & models
    • 31. Not inter-connected
    14
  • 32. The Web of Data: how?
    – we need to create a standard way of publishing Data on the Web (like HTML for docs)
    This is the Resource Description Framework (RDF)
    (a simple example here from Juan F. Sequeda), more next semester!)
    15
  • 33. Resource Description Framework (RDF)
    • A data model
    • 34. A way to model data
    • 35. Inspired form Relational databases and Logic
    • 36. RDF is a triple data model
    • 37. Labeled Graph (semantic networks)
    • 38. Subject, Predicate, Object
    <Isidoro> <was born in> <Chios>
    <Chios> <is part of> <Greece>
  • 39. The RDF Data Model
    Triples
    subject -> predicate -> object
    Tom -> worksFor -> Talis
    Talis -> basedIn -> Birmingham
    <uri> -> <uri> -> <uri> or "literal"
  • 40. παράδειγμα
    “Talis is Based Near Birmingham”
    <http://dbpedia.org/resource/Talis_Group>
    <http://xmlns.com/foaf/0.1/based_near>
    <http://sws.geonames.org/3333125/>
  • 41.
  • 42. Example: Document on the Web
  • 43. Databases back up documents
    THINGS have PROPERTIES:
    A Book as a Title, an author, …
    This is a THING:
    A book title “Programming the Semantic Web” by Toby Segaran, …
  • 44. Data representation in RDF
    Programming the Semantic Web
    title
    author
    book
    Toby Segaran
    isbn
    978-0-596-15381-6
    publisher
    name
    Publisher
    O’Reilly
  • 45. Everything on the web is identified by a URI!
  • 46. link the data to other data
    Programming the Semantic Web
    title
    author
    http://…/isbn978
    Toby Segaran
    isbn
    978-0-596-15381-6
    publisher
    name
    http://…/publisher1
    O’Reilly
  • 47. consider the data from Revyu.com
    hasReview
    http://…/review1
    http://…/isbn978
    description
    reviewer
    Awesome Book
    http://…/reviewer
    name
    Juan Sequeda
  • 48. start to link data
    hasReview
    http://…/review1
    http://…/isbn978
    Programming the Semantic Web
    title
    description
    sameAs
    hasReviewer
    Awesome Book
    author
    http://…/isbn978
    Toby Segaran
    http://…/reviewer
    name
    isbn
    978-0-596-15381-6
    Juan Sequeda
    publisher
    name
    http://…/publisher1
    O’Reilly
  • 49. Juan Sequeda publishes data too
    http://juansequeda.com/id
    http://dbpedia.org/Austin
    livesIn
    name
    Juan Sequeda
  • 50. Let’s link more data
    hasReview
    http://…/review1
    http://…/isbn978
    description
    hasReviewer
    Awesome Book
    http://…/reviewer
    name
    Juan Sequeda
    sameAs
    http://juansequeda.com/id
    http://dbpedia.org/Austin
    livesIn
    name
    Juan Sequeda
  • 51. And more
    hasReview
    http://…/review1
    http://…/isbn978
    Programming the Semantic Web
    title
    description
    sameAs
    hasReviewer
    Awesome Book
    author
    http://…/isbn978
    Toby Segaran
    http://…/reviewer
    name
    isbn
    978-0-596-15381-6
    Juan Sequeda
    publisher
    sameAs
    http://…/publisher1
    name
    O’Reilly
    http://juansequeda.com/id
    http://dbpedia.org/Austin
    livesIn
    name
    Juan Sequeda
  • 52. Linked data = internet + http + RDF
  • 53. Linked Data Principles
    Use URIs as names for things
    Use URIs so that people can look up (dereference) those names.
    When someone looks up a URI, provide useful information.
    Include links to other URIs so that they can discover more things.
  • 54. Web as a database
    Linked Data makes the web exploitable as ONE GIANT HUGE GLOBAL DATABASE!Is there any query language like sql?SPARQL… (next semester)
  • 55. History of LD
    • Linked Data Design Issues by TimBL July 2006
    • 56. Linked Open Data Project WWW2007
    • 57. First LOD Cloud May 2007
    • 58. 1st Linked Data on the Web Workshop WWW2008
    • 59. 1stTriplification Challenge 2008
    • 60. How to Publish Linked Data Tutorial ISWC2008
    • 61. BBC publishes Linked Data 2008
    • 62. 2nd Linked Data on the Web Workshop WWW2009
    • 63. NY Times announcement SemTech2009 - ISWC09
    • 64. 1st Linked Data-a-thon ISWC2009
    • 65. 1st How to Consume Linked Data Tutorial ISWC2009
    • 66. Data.gov.uk publishes Linked Data 2010
    • 67. 2st How to Consume Linked Data Tutorial WWW2010
    • 68. 1st International Workshop on Consuming Linked Data COLD2010
    • 69. El.dbpedia.org
  • May 2007
  • 70.
  • 71. What is a Linked Data application/service?
    Software system that makes use of data on the Web from multiple datasets and that benefits from links between the datasets
  • 72. Characteristics of Linked Data Applications
    • Consume data that is published on the web following the Linked Data principles: an application should be able to request, retrieve and process the accessed data
    • 73. Discover further information by following the links between different data sources: the fourth principle enables this.
    • 74. Combine the consumed linked data with data from sources (not necessarily Linked Data)
    • 75. Expose the combined data back to the web following the Linked Data principles
    • 76. Offer value to end-users
  • the 5 stars of open linked data
    ★make your stuff available on the Web (whatever format)
    ★★make it available as structured data (e.g. excel instead of image scan of a table)
    ★★★non-proprietary format (e.g. csv instead of excel)
    ★★★★use URLs to identify things, so that people can point at your stuff
    ★★★★★link your data to other people’s data to provide context
    http://lab.linkeddata.deri.ie/2010/star-scheme-by-example/
  • 77. Examples
    • Data.gov.uk
    • 78. http://wheredoesmymoneygo.org/
    • 79. http://energy.publicdata.eu/ee/vis.html
    • 80. Greece – not in Linked Data!
    • 81. http://geodata.gov.gr/geodata/
    • 82. Fuelprices.gr
    • 83. E-prices.gr
    • 84. Et.diavgeia.gov.gr
  • 40
  • 85. 41
  • 86. More Examples
    http://data-gov.tw.rpi.edu/wiki
    http://dbrec.net/
    http://fanhu.bz/
    http://data.nytimes.com/schools/schools.html
    http://sig.ma
    http://visinav.deri.org/semtech2010/