entailment vs Inference

Artificial Intelligence: A Modern Approach

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http://www.isle.org/~sbay/ics171/notes/entailment Entailment vs Inference KB entails alpha means that if the KB is true then so must alpha. KB |- alpha (i.e. alpha can be infered from KB) just means that with some inference procedure we can derive alpha. The difference between entailment and inference is that inference procedures cannot necessarily find everything that can be entailed and inference procedures are not necessarily correct/sound (i.e. can derive things that aren't necessarily true). For example, the abduction rule states: P => Q, Q cavities cause toothaches, I have a toothache
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Unformatted text preview: --------- -------------------------------------------P therefore I have a cavity This is an example of unsound inference. Although this type of reasoning can be useful, P is not necessarily true (i.e. the KB does not entail P) -- there could be another cause of the toothache. The example with Phd's and salary earnings at the end of the lecture notes on FOL is an example where Modus Ponens cannot find everything that is entailed by the KB (i.e. Modus Ponens cannot infer rich(ME), but resolution can). http://www.isle.org/~sbay/ics171/notes/entailment [2/4/2008 5:27:36 PM]...
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This document was uploaded on 02/05/2008.

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