Logical formalisms

Version 1 (Benjamin Johnston, 07/21/2011 09:42 am)

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h1. Logical formalisms
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The precursory ideas of McCarthy's Advice Taker were developed by "McCarthy and Hayes":http://www-formal.stanford.edu/jmc/mcchay69.pdf into the Situation Calculus: a logical formalism for reasoning about real-life situations. These ideas later motivated the development of the "Event Calculus":http://www.doc.ic.ac.uk/~rak/papers/event%20calculus.pdf and a range of other action and fluent-based calculi. In such formalisms, events, world-states, actors, properties and physical entities are denoted by the objects, terms and functors of a symbolic logic. These formalisms therefore operate over an assumed domain of pre-categorized knowledge and actions are defined in terms of the changing properties of an environment. 
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For example, the following expression may be used to express that when someone drops a book in a room, that book can then be found in that room (Section 6.47 of "Commonsense Reasoning":http://www.amazon.com/dp/0123693888):
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HoldsAt(InRoom(a,r),t) =>
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Initiates(LetGoOf(a,o), InRoom(o,r), t)
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Action logics have found wide application in intelligent systems. For example:
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* "General game playing":http://games.stanford.edu/, wherein systems must discover strategies and compete in novel games without human oversight
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* "One-touch-mission systems":http://www.ida.liu.se/~giaco/publications/publications/2006/Navigation_2006.pdf, requiring the ability to modify plans on the fly when obstacles or problems are encountered
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* "Intelligent characters":http://www.martinmagnusson.com/publications/magnusson-doherty-2008c.pdf in computer games that must communicate with human beings and independently discover plans to achieve their own ends