Linked Data

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presented at Practical Semantic Astronomy 2009

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  • Linked Data

    1. 1. Linking Open Data <ul><ul><li>Danny Ayers </li></ul></ul><ul><ul><li>SemAst2009 </li></ul></ul>
    2. 2. Obligatory Children Slide
    3. 3. Credits: <ul><ul><li>Many slides derived from those of </li></ul></ul><ul><ul><li>Tom Heath, Michael Hausenblas, Chris Bizer, Richard Cyganiak, Olaf Hartig </li></ul></ul>
    4. 4. Quote <ul><ul><li>Linked Data is the Semantic Web done right, and the Web done right.” </li></ul></ul><ul><ul><li>- Tim Berners-Lee </li></ul></ul>
    5. 5. <ul><li>Introduce the concept of Linked Data </li></ul><ul><li>Highlight why you would want to publish Linked Data on the Web </li></ul><ul><li>Introduce the principles and best practices of publishing Linked Data on the Web </li></ul><ul><li>Demonstrate the creation and consumption of Linked Data </li></ul><ul><li>Answer your burning Linked Data publishing questions </li></ul>Objectives
    6. 6. Overview <ul><li>From a Web of Documents to a Web of Data </li></ul><ul><ul><li>Web APIs, Microformats, and Linked Data </li></ul></ul><ul><li>Linked Data Deployment on the Web </li></ul><ul><ul><li>What data is out there? </li></ul></ul><ul><li>Applications </li></ul><ul><ul><li>What is being done with the data? </li></ul></ul>
    7. 7. Classic Data : in silos Image: Bob Jagensdorf, http://flickr.com/photos/darwinbell/, CC-BY
    8. 8. The Classic Web <ul><li>Single global information space </li></ul><ul><li>URLs as </li></ul><ul><ul><li>globally unique IDs </li></ul></ul><ul><ul><li>retrieval mechanism </li></ul></ul><ul><li>HTML as shared content format </li></ul><ul><li>Hyperlinks </li></ul><ul><li>Shortcomings </li></ul><ul><li>Content is not well structured </li></ul><ul><li>You can not ask expressive queries </li></ul><ul><li>You can not process content within applications </li></ul>B C HTML HTML HTML Web Browsers Search Engines hyper- links A
    9. 9. What do we actually want? Use the Web like a single global database.
    10. 10. Solution <ul><li>Web APIs </li></ul><ul><li>Microformats </li></ul><ul><li>Linked Data </li></ul>Publish structured data directly on the Web Different Approaches
    11. 11. Web APIs
    12. 12. Mashups <ul><li>Positive </li></ul><ul><li>APIs expose structured data </li></ul><ul><li>APIs enable new applications </li></ul><ul><li>Negative </li></ul><ul><li>Usually proprietary interfaces </li></ul><ul><li>Mashups are based only on fixed set of sources </li></ul><ul><li>You can't usually set hyperlinks between data objects </li></ul>Mashup Up Web API A Web API B Web API C Web API D
    13. 13. Web APIs slice the Web into separate data silos Image: Bob Jagensdorf, http://flickr.com/photos/darwinbell/, CC-BY
    14. 14. What do we want? Use the Web as a single global database using what we know works on the Web
    15. 15. Connecting Worlds One Web! Data Documents
    16. 16. What works on the Web? <ul><li>Uniform Identifiers (URIs) </li></ul><ul><li>Common Interface Protocol (HTTP) </li></ul><ul><li>Standard Representation Formats (HTML, Atom/RSS etc) </li></ul>
    17. 17. What works on the Web? <ul><li>The Hyperlink </li></ul>
    18. 18. Evolving the Link <ul><li><a href=” http://example.org/home.html “> </li></ul><ul><li>Home Page </li></ul><ul><li></a> </li></ul>page.html home.html
    19. 19. Evolving the Link <ul><li><a href=”http://example.org/home.html” </li></ul><ul><li>rel=”home”> </li></ul><ul><li>Home Page </li></ul><ul><li></a> </li></ul>page.html home.html home
    20. 20. Microformats <ul><li>Embed structured data into HTML pages. </li></ul><ul><li>hCard, hCalender, hReview, XFN, … </li></ul><ul><li>Compatible with the idea of the Web as single information space. </li></ul><ul><li>Shortcomings </li></ul><ul><ul><li>Only a fixed set of microformats exist </li></ul></ul><ul><ul><li>No direct way to connect data items </li></ul></ul><div class=&quot;vevent&quot;> <span class=&quot;summary&quot;>bdigital</span> <abbr class=&quot;dtstart&quot; title=&quot;2008-05-20&quot;>May 20</abbr> - <abbr class=&quot;dtend&quot; title=&quot;2007-05-22&quot;>22</abbr> </div>
    21. 21. Evolving the Link <ul><li><rdf:Description </li></ul><ul><ul><li>rdf:about=” http://example.org/page ”> </li></ul></ul><ul><li><x:home </li></ul><ul><ul><li>rdf:resource=” http://example.org/home ” /> </li></ul></ul><ul><li></rdf:Description> </li></ul>page home x:home
    22. 22. Linked Data B C Thing typed links A D E typed links typed links typed links Thing Thing Thing Thing Thing Thing Thing Thing Thing <ul><li>Use Semantic Web technologies to </li></ul><ul><li>publish structured data on the Web, </li></ul><ul><li>set links between data from one data source to data within other data sources . </li></ul>
    23. 23. RDF Relations <ul><li><rdf:Description </li></ul><ul><ul><li>rdf:about=” http://example.org/page ”> </li></ul></ul><ul><li><x:home </li></ul><ul><ul><li>rdf:resource=” http://example.org/home ” /> </li></ul></ul><ul><li></rdf:Description> </li></ul>x:home subject object http://example.org /page ... http://example.org /home ...
    24. 24. Identifiers <ul><li>Identification by Description </li></ul><ul><li>Non-HTTP URIs </li></ul><ul><li>HTTP URIs </li></ul>
    25. 25. Linked Data Principles <ul><li>Use URIs as names for things </li></ul><ul><li>Use HTTP URIs so that people can look up those names. </li></ul><ul><li>When someone looks up a URI, provide useful information. </li></ul><ul><li>Include links to other URIs. so that they can discover more things. </li></ul><ul><li>Tim Berners-Lee 2007 </li></ul><ul><li>http://www.w3.org/DesignIssues/LinkedData.html </li></ul>
    26. 26. The RDF Data Model Richard Cyganiak dbpedia:Berlin foaf:name foaf:based_near foaf:Person rdf:type pd:cygri
    27. 27. Data objects are identified with HTTP URIs pd:cygri Richard Cyganiak dbpedia:Berlin foaf:name foaf:based_near foaf:Person rdf:type pd:cygri = http://richard.cyganiak.de/foaf.rdf#cygri dbpedia:Berlin = http://dbpedia.org/resource/Berlin
    28. 28. Follow Your Nose... Richard Cyganiak dbpedia:Berlin foaf:name foaf:based_near foaf:Person rdf:type pd:cygri dp:Cities_in_Germany 3.405.259 dp:population skos:subject
    29. 29. Dereferencing URIs over the Web Richard Cyganiak dbpedia:Berlin foaf:name foaf:based_near foaf:Person rdf:type dbpedia:Hamburg dbpedia:Muenchen skos:subject skos:subject pd:cygri dp:Cities_in_Germany 3.405.259 dp:population skos:subject
    30. 30. Universal Connector <resourceB> rdfs:seeAlso <resourceA>
    31. 31. Universal Connector <resourceB> rdfs:seeAlso <resourceA> foaf:Person rdf:type
    32. 32. Take Care! <resourceB> owl:sameAs <resourceA>
    33. 33. The Disco – Hyperdata Browser
    34. 35. Semantic Web Specifications <ul><li>HTTP + URIs </li></ul><ul><li>RDF + RDFs </li></ul><ul><li>OWL </li></ul><ul><li>SKOS </li></ul><ul><li>SPARQL </li></ul><ul><li>RDFa </li></ul><ul><li>GRDDL </li></ul><ul><li>Turtle/N3 </li></ul>Coming soon: POWDER, OWL2, RIF
    35. 36. What of Web Services? “ Web APIs Are Just Web Sites” - Paul Downey Linked Data is exposed as (very simple) RESTful services
    36. 37. What of RDF Stores? A triplestore is just a cache of a chunk of the Semantic Web Convenient for data merging, querying (SPARQL) and inference See also: Semantic Web Client Library
    37. 38. What of the Real World? source: http://danbri.org/words/2008/04/15/300 based on timbl 1994
    38. 39. W3C Linking Open Data Project <ul><li>Community effort to </li></ul><ul><ul><li>publish existing open license datasets as Linked Data on the Web </li></ul></ul><ul><ul><li>interlink things between different data sources </li></ul></ul>
    39. 40. LOD Datasets on the Web: May 2007
    40. 41. LOD Datasets on the Web: August 2007
    41. 42. LOD Datasets on the Web: February 2008
    42. 43. LOD Datasets on the Web: September 2008
    43. 44. LOD Datasets on the Web: March 2009
    44. 45. Spotlight: Geonames <ul><li>over 8 million geographical locations </li></ul><ul><li>feature hierarchy </li></ul>
    45. 46. Spotlight: DBpedia <ul><li>extracts structured data from Wikipedia. </li></ul><ul><li>covers over 2.2 million concepts from various domains. </li></ul>
    46. 47. Example RDF Links <ul><li>RDF links from DBpedia to other data sources </li></ul><ul><li>RDF link from a FOAF profile to DBpedia </li></ul><http://dbpedia.org/resource/Berlin> owl:sameAs <http://sws.geonames.org/2950159> . <http://richard.cyganiak.de/foaf.rdf#cygri> foaf:topic_interest <http://dbpedia.org/resource/Semantic_Web> . <http://dbpedia.org/resource/Tim_Berners-Lee> owl:sameAs <http://www4.wiwiss.fu-berlin.de/dblp/resource/person/100007> .
    47. 48. <ul><li>Universities and Research Institutes </li></ul><ul><ul><li>Massachusetts Institute of Technology (USA) </li></ul></ul><ul><ul><li>University of Southampton (UK) </li></ul></ul><ul><ul><li>Freie Universität Berlin (DE) </li></ul></ul><ul><ul><li>DERI (IRE) </li></ul></ul><ul><ul><li>KMi, Open University (UK) </li></ul></ul><ul><ul><li>University of London (UK) </li></ul></ul><ul><ul><li>Universität Hannover (DE) </li></ul></ul><ul><ul><li>University of Pennsylvania (USA) </li></ul></ul><ul><ul><li>Universität Leipzig (DE) </li></ul></ul><ul><ul><li>Universität Karlsruhe (DE) </li></ul></ul><ul><ul><li>Joanneum (AT) </li></ul></ul><ul><ul><li>University of Toronto (CA) </li></ul></ul>Organizations publishing Linked Data <ul><li>Companies </li></ul><ul><ul><li>BBC (UK) </li></ul></ul><ul><ul><li>OpenLink (UK) </li></ul></ul><ul><ul><li>Zitgist (USA) </li></ul></ul><ul><ul><li>Talis (UK) </li></ul></ul><ul><ul><li>Garlik (UK) </li></ul></ul><ul><ul><li>Mondeca (FR) </li></ul></ul><ul><ul><li>Cyc Foundation (USA) </li></ul></ul>
    48. 49. Applications B C Thing typed links A D E typed links typed links typed links Thing Thing Thing Thing Thing Thing Thing Thing Thing Search Engines Linked Data Mashups Linked Data Browsers <ul><li>What can I do with this? </li></ul>
    49. 50. Linked Data Browsers <ul><li>Tabulator Browser (MIT, USA) </li></ul><ul><li>Marbles (FU Berlin, DE) </li></ul><ul><li>OpenLink RDF Browser (OpenLink, UK) </li></ul><ul><li>Zitgist RDF Browser (Zitgist, USA) </li></ul><ul><li>Disco Hyperdata Browser (FU Berlin, DE) </li></ul><ul><li>Fenfire (DERI, Irland) </li></ul>
    50. 51. Tabulator
    51. 52. Linked Data Mashups <ul><li>Domain-specific applications </li></ul><ul><li>- using Linked Data from the Web </li></ul>
    52. 53. DBpedia Mobile <ul><li>Geospatial entry point into the Web of Data </li></ul><ul><li>Starts with DBpedia, Revyu and Flickr data </li></ul>
    53. 54. Web of Data Search Engines <ul><li>Falcons (IWS, China) </li></ul><ul><li>Sindice (DERI, Ireland) </li></ul><ul><li>MicroSearch (Yahoo, Spain) </li></ul><ul><li>Watson (Open University, UK) </li></ul><ul><li>SWSE (DERI, Ireland) </li></ul><ul><li>Swoogle (UMBC, USA) </li></ul>
    54. 55. Falcons
    55. 56. Why publish Linked Data on the Web? <ul><li>Your data becomes part of a single global data space (the Web of Data = Semantic Web) </li></ul><ul><li>People can use various data browsers to explore your data </li></ul><ul><li>Your data is crawled by Semantic Web search engines and can be used by independent applications </li></ul><ul><li>People start setting links to your data, which allows more people to find and use your data </li></ul>
    56. 57. Why publish Linked Data on the Web? <ul><li>Linked Data builds on the classic architecture of the Web </li></ul><ul><li>Linked Data is more generic then Web APIs or Microformats </li></ul><ul><ul><li>Builds on standards in contrast to proprietary Web APIs </li></ul></ul><ul><ul><li>Enables applications that work against an unbound set of data sources and incorporate new data sources as they become available on the Web </li></ul></ul>
    57. 58. Linked Data Principles <ul><li>Use URIs as names for things </li></ul><ul><li>Use HTTP URIs so that people can look up those names. </li></ul><ul><li>When someone looks up a URI, provide useful information. </li></ul><ul><li>Include links to other URIs. so that they can discover more things. </li></ul><ul><li>Tim Berners-Lee 2007 </li></ul><ul><li>http://www.w3.org/DesignIssues/LinkedData.html </li></ul>
    58. 59. Example : Source Data
    59. 60. Example : First Pass @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . @prefix owl: <http://www.w3.org/2002/07/owl#> . @prefix x: <http://purl.org/stuff/astro#> . x:Megrez rdf:type x:A3_dwarf ; x:magnitude &quot;3.1&quot; ; x:partOf [ rdf:type x:Constellation ; x:hasName &quot;Ursa Major&quot; ] . (RDF Turtle/N3 Syntax)
    60. 61. Example : Vocabulary @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . @prefix x: <http://purl.org/stuff/astro#> . x:Star rdf:type rdfs:Class . x:Constellation rdf:type rdfs:Class . x:A3_Dwarf rdfs:subClassOf x:Star . x:magnitude rdf:type rdf:Property . x:partOf rdf:type rdf:Property . x:hasName rdf:type rdf:Property .
    61. 62. But... <ul><li>Use URIs as names for things </li></ul><ul><li>Use HTTP URIs so that people can look up those names. </li></ul><ul><li>When someone looks up a URI, provide useful information. </li></ul><ul><li>Include links to other URIs. so that they can discover more things. </li></ul>Existing vocabularies and resource URIs are likely to be well-linked already – reuse is good!
    62. 63. Example : Better Linkage @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> . @prefix x: <http://purl.org/stuff/astro#> . @prefix astro: <http://archive.astro.umd.edu/ont/astronomy.owl#> . @prefix foaf: <http://xmlns.com/foaf/0.1/> . @prefix dolce: <http://www.loa-cnr.it/ontologies/DOLCE-Lite.owl#> . @prefix dbpedia: <http://dbpedia.org/resource/> . dbpedia:Delta_Ursae_Majoris rdf:type x:A3_Dwarf ; foaf:name &quot;Megrez&quot;; x:magnitude &quot;3.1&quot; ; dolce:part-of dbpedia:Ursa_Major ; rdfs:seeAlso <http://www.dcs.gla.ac.uk/workshops/semast09> . dbpedia:Ursa_Major rdf:type astro:Constellation .
    63. 64. Mass-Publication Techniques <ul><li>Generally either: </li></ul><ul><li>bulk conversion </li></ul><ul><li>live mapping from existing databases </li></ul>
    64. 65. New Vocabularies : voiD Vocabulary of Interlinked Datasets Classes: Dataset | Linkset | TechnicalFeature | Properties: statItem | feature | subset | target | sparqlEndpoint | linkPredicate | exampleResource | vocabulary | subjectsTarget | objectsTarget | dataDump | uriLookupEndpoint | uriRegexPattern |
    65. 66. New Vocabularies : Scovo Statistical Core Vocabulary
    66. 67. &quot;It is important to look as it as an interconnection bus, and it hasn't started working in earnest until one person's data is being used by some other unplanned use. This unexpected reuse is the measure.&quot; - Tim Berners-Lee, re. State of the Semantic Web Finishing Quotes
    67. 68. &quot;Engineer for serendipity.&quot; - Roy T. Fielding, re. REST Finishing Quotes
    68. 69. http://hyperdata.org/astronomy/ Related Links etc.

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