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The problem of 'implicit knowledge'

Mark Birbeck's picture
Submitted by Mark Birbeck on Tue, 2006-05-02 13:06.

As it happens, relying on implicit knowledge is exactly what goes on in many situations; processors and systems get round the skewed nature of this embedded metadata by having some implicit knowledge about what they are processing.

For example, if I submitted my home page to a web-site that allows people to search for bloggers in different locations, then the web-site could pretty much assume that it was dealing with a person's location. It could therefore impute the following from my metadata:

  @prefix dc:  <http://purl.org/dc/elements/1.1/> .

  <http://internet-apps.blogspot.com> dc:creator
    [
      foaf:name "Mark Birbeck";
      geo:lat "43.95";
      geo:long "4.833333"
    ] .

I've used N3 again to represent the meaning--and properties from existing vocabularies, as available--but in plain language what we have is this:

  • a resource identified by http://internet-apps.blogspot.com
    • was created by 'something' (we're not quite sure what)
      • that has a name of Mark Birbeck
      • and a location of Avignon, in the south of France.

But just to be very clear, there is nothing in our original mark-up that says that the set of statements I just derived is a legitimate interpretation:

  <head>
    <meta name="author" content="Mark Birbeck" />
    <meta name="geo.position" content="43.95;4.833333" />
  </head>

It is only because the web-site instructed me to mark-up my documents in exactly this way so as to convey my current location that it works; I could have created a web-page for a house, and put in location data in exactly the same format before submitting it to a completely different web-site concerning real estate, and that site would have decided to use my information to represent a house for sale, rather than my current location.

In short, if we received this mark-up out of context then all we could say with any certainty is that something has a location of 43.95, 4.833333--our browser extension can show you where in the world that is, but what else you make of this information is entirely up to you!

(Some people will argue that you always have metadata in a context, so this is not a problem. This is in some ways true, but the problem with solutions like microformats is that you need to create all possible contexts in advance of them occurring...which just does not scale for a decentralised, organic, semantic web.)

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