We have two set of clauses:
$S1 = \left \{ P(x),a \right \} $ and $S2 = \left \{ P(y),b \right \} $
I have two questions:
1)Why it's possible to represent a clause with only a constant ?( im speaking about the constants a and b) Since constants are not predicates, what is the meaning of a clause with only a constant inside ?
2)How it's possibile to unificate this 2 sets since $a\neq b$ ?