Introduction to Logic
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Exercise 14.9 - Resolution

Use resolution to show that the clauses {¬p(x,y), q(x,y,f(x,y))}, {¬r(y,z), q(a,y,z)}, {r(y,z), ¬q(a,y,z)}, {p(x,g(x)), q(x,g(x),z)}, and {¬r(x,y), ¬q(x,w,z)} are unsatisfiable. This one is a little tricky. Be careful about factoring.

Robinson
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Objects: a, b, c
Functions: f, g
Goal  Incomplete

















1 {~p(X,Y),q(X,Y,f(X,Y))} Premise 2 {~r(Y,Z),q(a,Y,Z)} Premise 3 {r(Y,Z),~q(a,Y,Z)} Premise 4 {p(X,g(X)),q(X,g(X),Z)} Premise 5 {~r(X,Y),~q(X,W,Z)} Premise 6 {~q(a,X,Y),~q(X,W,Z)} Resolution 3 5 7 {q(X,g(X),V34),q(X,g(X),f(X,g(X)))} Resolution 4 1 8 {q(X,g(X),f(X,g(X)))} Factoring 7 9 {~q(a,X,Y)} Resolution 8 6 10 {} Resolution 8 9