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537Re: [aima-talk] chapter 7 resolution algorithm

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  • Ivan Villanueva
    Sep 7, 2005
      On Mon, Sep 05, 2005 at 04:27:31PM +0200, Ivan Villanueva wrote:
      > on chapter 7, figure 7.13, the PL-RESOLUTION algorithm is proposed with a
      > helper function, PL-RESOLVE, that returns the set of all possible
      > clauses obtained by resolving two inputs.
      > However, on the previous page the resolution rule is described removing
      > all complementary literals at one.

      That is not the case. Sorry.

      > I wonder if PL-RESOLVE should just remove all complementary literals and
      > returns just a clause with the remaining literals.

      Of course not. The resolution rule allows to discard two complementary literals,
      but not more at one.
      For example with the two sentences:

      ~P1,2 | ~P2,1 | B1,1 ~B1,1 | P1,2 | P2,1

      one can apply the resolution rule and get:

      ~P1,2 | ~P2,1 | P1,2 | P2,1

      but not an empty clause.

      Ivan Villanueva :-)
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