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Experiments in Linked Data

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An overview of various private experiments to implement Linked Data using Ontopia.

An overview of various private experiments to implement Linked Data using Ontopia.

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  • 1. Experiments in linked data
    Lars Marius Garshol, <larsga@bouvet.no>
    Topic Maps 2010, Oslo, 2010-04-15
    http://twitter.com/larsga
  • 2. What is this talk about?
    Connecting across applications
    using common identifiers for subjects
    The applications are
    tmphoto photo gallery
    tmtools Topic Maps tools index
    Larsblog my private blog
    tmcase1 Naito-san’s index of Topic Maps talks
    ontopia.net the new Ontopia web site (not live yet)
  • 3. Why experiments?
    I prefer to talk about real projects
    but linked data has been hard to sell to customers
    because the concept is hard to grasp?
    because collaboration between organizations is hard?
    because the market wasn’t ready yet?
    anyway, there are very few projects so far
    Therefore I’m showing some private experiments instead
    the scale and complexity are limited
    but it does demonstrate some of the potential
  • 4. A lightning tutorial
    Identifiers
  • 5. Identifiers?
    PSIs (Published Subject Identifiers)
    a part of the Topic Maps standard, used for merging
    a URI attached to a topic to identify it
    the URI should refer to a page defining the subject
    T
    http://psi.ontopedia.net/Lars_Marius_Garshol
  • 6. Name
    Definition
  • 7. PSIs – things to note
    Anyone can make a PSI
    as long as they can publish content on the web
    Domain names ensure PSIs are globally unique
    only I make PSIs starting http://psi.garshol.priv.no/
    PSIs can identify anything
    if you can imagine it, you can make a PSI for it
  • 8. Starting with the first application
    So, to the experiments
  • 9. tmphoto
    Category
    Person
    Photo
    Event
    Location
    http://www.garshol.priv.no/tmphoto/
    A topic map to organize my personal photos
    contains ~15,000 photos
    A web gallery runs on Ontopia
    on www.garshol.priv.no
  • 10. You need more than one application to have true linked data. Data inside a single application is of course linked, but only in a trivial sense.
    No linked data at this point
  • 11. tmtools
    http://www.garshol.priv.no/tmtools/
    Organization
    An index of Topic Maps tools
    organized as shown on the right
    Again, web application for browsing
    screenshots below
    Person
    Software
    product
    Platform
    Category
    Technology
  • 12. The person page
    Boring! No content.
  • 13. And in tmphoto...
  • 14. get-illustration
    A web service in tmphoto
    receives the PSI of a person
    then automatically picks a suitable photo of that person
    Based on
    vote score for photos,
    categories (portrait),
    other people in photo
    ...
    The service returns
    a topic map fragment with links to the person page and a few different sizes of the selected photo
    http://www.garshol.priv.no/blog/183.html
  • 15. get-illustration
    Hmmm. Scores, categories, people in photo, ...
    Do you have a photo of
    http://psi.ontopedia.net/Benjamin_Bock ?
    http://www.garshol.priv.no/tmphoto/get-illustration?identifier=http://psi.on....
    tmphoto
    tmtools
    Topic map
    fragment
  • 16. Voila...
  • 17. Points to note
    No hard-wiring of links
    just add identifiers when creating people topics
    photos appear automatically
    if a better photo is added later, it’s replaced automatically
    No copying of data
    no duplication, no extra maintenance
    Very loose binding
    nothing application-specific
    Highly extensible
    once the identifiers are in place we can easily pull in more content from other sources
  • 18. How to choose common identifiers?
    I was of course able to use the same PSI because I produced both datasets
    But what if the two applications were maintained by different people?
    Subj3ct.com solves that problem
    search on Subj3ct to find global identifiers for your subjects
  • 19.
  • 20. Overview
    tmtools
    tmphoto
    get-illustration
  • 21. Now what?
    So far, so good
  • 22. My blog
    Has more content about
    people (tmphoto & tmtools),
    events (tmphoto),
    tools (tmtools),
    technologies (tmtools)
    Should be available in those applications
  • 23. Solution
    My blog posts are tagged
    but the tags are topics, which can have PSIs
    these PSIs are used in tmphoto and tmtools, too
    The get-topic-page request lets tmphoto & tmtools ask the blog for links to relevant posts
    given identifiers for a topic, returns links to pages about that topic
    http://www.garshol.priv.no/blog/145.html
  • 24. get-topic-page
    Do you have pages about
    http://psi.ontopedia.net/TMRA_2008 ?
    http://www.garshol.priv.no/blog/get-topic-page?identifier=http://psi.on....
    Blog
    tmphoto
    Topic map
    fragment
    Topics linking to
    individual blog posts
  • 25. In tmphoto
  • 26. Overview
    tmtools
    tmphoto
    get-illustration
    get-topic-page
    blog
  • 27. Easy next steps
    Topic pages on the blog must link to tmtools and tmphoto
    trivial to do via get-topic-page
    And the blog can use get-illustration, too
    and so can ontopia.net and tmcase1
    Oh, and they should link to the blog and the other applications...
  • 28. After a little hacking...
    What a mess!
    tmcase1
    tmtools
    tmphoto
    ontopia.net
    blog
    get-topic-page
    get-illustration
  • 29. We need a clean-up here
    The get-topic-page service is generic
    that is, it’s not tied to any specific application
    further, the result set is a topic map fragment
    Topic maps can be merged as we know
    So, we could make a hub service
    basically, a get-topic-page aggregator
  • 30. Client app #2
    Client app #1
    Client app #3
    How it works
    Hub service
    blog
    tmcase1
    tmtools
    tmphoto
    ontopia.net
  • 31. Benefits of this approach
    Much cleaner architecture
    overview diagram no longer looks like a bowl of spaghetti
    Easier to maintain
    if I want to add/remove a service I do it in a single place
    Safer
    the hub service insulates clients from slow/unresponsive servers
  • 32. The result
  • 33. Subj3ct.com
    Subj3ct is not just a database of PSIs
    it also has links to pages with more information about the subjects
    this can easily be wrapped in a get-topic-page service
    http://api.subj3ct.com/
    subjects
    get-topic-page
    Subj3ct
    Wrapper
    service
    Client
  • 34. So we can add Subj3ct...
    Client app #2
    Client app #1
    Client app #3
    Hub service
    blog
    tmcase1
    tmtools
    tmphoto
    ontopia.net
    Subj3ct
  • 35. There is much more to tell
    Unfortunately, 35 minutes is not very much
    and this stuff takes some explaining
    So I had to omit
    sharing data with TMSync
    manual reuse of data with the Ontopoly editor
    ...
    Maybe next year
  • 36. Conclusion
    Linked data is technically easy
    conceptually and politically it’s harder
    All you really need is
    shared PSIs on your topics, and
    someone to connect with
    Subj3ct.com is crucial
    ensures that different players pick the same PSIs independently
    without this there is no connecting...