Task: Sentence Expansion
Input (English): A Horn clause with exactly one positive literal is a definite clause ; a definite clause with no negative literals is sometimes called a “ fact ” ; and a Horn clause without a positive literal is sometimes called a goal clause .
Output (English): A Horn clause with exactly one positive literal is a definite clause or a strict Horn clause ; a definite clause with no negative literals is sometimes called a unit clause , and a unit clause without variables is sometimes called a fact ; and a Horn clause without a positive literal is sometimes called a goal clause ( note that the empty clause consisting of no literals is a goal clause ) .