Among the following which is not a horn clause?

Among the following which is not a horn clause?

    • p
    • Øp V q
    • p → q
    • p → Øq

Horn Clause

The definite clause language does not allow a contradiction to be stated. However, a simple expansion of the language can allow proof by contradiction.

An integrity constraint is a clause of the form


where the ai are atoms and false is a special atom that is false in all interpretations.

A Horn clause is either a definite clause or an integrity constraint. That is, a Horn clause has either false or a normal atom as its head.

Integrity constraints allow the system to prove that some conjunction of atoms is false in all models of a knowledge base - that is, to prove disjunctions of negations of atoms. Recall that ¬p is the negation of p, which is true in an interpretation when p is false in that interpretation, and p∨q is the disjunction of p and q, which is true in an interpretation if p is true or q is true or both are true in the interpretation. The integrity constraint false←a1∧...∧ak is logically equivalent to ¬a1∨...∨¬ak.

Your can read more here with examples.

If you think above Mcq is wrong then please leave us comment with correct answers!

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