Which of the following is a HORN CLAUSE?
A Horn clause is a disjunction of literals with at most one positive literal (e.g., A ^ B -> C == ~A v ~B v C).
What is the Most General Unifier (MGU) of atomic sentences P(a, x, f(g(y))) and P(z, f(z), f(w))?
$Unifying: z=a. Next, x=f(z)=f(a). Next, f(g(y))=f(w) => w=g(y). MGU = {z/a, x/f(a), w/g(y)}.$
The 2-SAT problem can be solved in linear time O(N + M) using:
2-SAT converts clauses (A v B) into implications (~A -> B, ~B -> A) and checks if x and ~x belong to the same SCC.
A propositional formula is a TAUTOLOGY if and only if:
A tautology evaluates to True for all $2^n$ rows of its truth table.
Modus Ponens is the inference rule that states:
Modus Ponens: if premise P holds and implication P -> Q holds, conclusion Q must hold.