Slide 14.8: Resolution
Slide 14.10: Examples of resolution
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Resolution (Cont.)

Another way of looking at resolution is to combine left-hand and right-hand sides of both Horn clauses and then cancel those statements that match on both sides. Thus, for the simplest example, combine the two clauses to give 
     b, c ← a, b.
and canceling the b, 
     b, c ← a, b.
gives 
     c ← a.
An Example
The simplest case is when the goal is already a known fact, such as 
     mammal( human ).
and one asks whether a human is a mammal: 
     ← mammal( human ).
Using resolution, the system combines the two Horn clauses into 
     mammal( human ) ← mammal( human ).
and then cancels both sides to obtain 
     ←
Thus, the system has found that indeed a human is a mammal and would respond to the query with “Yes.”