Wednesday, December 27, 2006

Keeping track of Context in Life and on the Web 

The Sun BabelFish Blog : Weblog: "Decontextualised information is useful, and on the web more so that in other places, but it is not without drawbacks.
Decontextualising information makes it a lot longer. I can say 'This house is big', but if I wanted to decontexualise it properly I would have to give information as to where the house is located, at what time of the house's existence this was the case, and in relation to what the predicate big was applicable.
Also, surprisingly, complete decontextualisation of information in fact looses some information. So if I give you a map of the Paris underground when you ask me where you are, you will have all the information you need, but one essential piece will be missing, your relation to the map: where you currently are, your context. If you call the talking clock, you want to know the time now, not the time it was at the time it was that time, which would be completely uninformative.
Finally deciding on the best framework for decontextualising all data, what some seem to call an upper ontology, is work in progress, and it is quite possible that there may never be a final one, as such work itself takes place in a context, which may be the object of future assertions. In any case we always have Gödel's incompleteness theoremto take account of, which says that there can be no final compelete theory of anything."

Sunday, December 24, 2006

Situation Theory and Situation Semantics 

Situation Theory and Situation Semantics (PDF file)
by Keith Devlin

from the Introduction:

"In their 1980 paper The Situation Underground, the first published work
on situation semantics, Barwise and Perry wrote of situations:

'The world consists not just of objects, or of objects, properties and
relations, but of objects having properties and standing in relations
to one another. And there are parts of the world, clearly recognized
(although not precisely individuated) in common sense and human
language. These parts of the world are called situations. Events and
episodes are situations in time, scenes are visually perceived situations,
changes are sequences of situations, and facts are situations
enriched (or polluted) by language.'

The appearence of the word 'parts' in the above quotation is significant. Situations are parts of the world and the information an agent has about a given situation at any moment will be just a part of all the information that is theoretically available. The emphasis on partiality contrasts situation semantics from what was regarded by many as its principal competitor as a semantic theory, possible worlds semantics."

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