UGC NET CSE | June 2013 | Part 3 | Question: 34

Question

Horn clauses are special kinds of propositions which can be described as

• A. Single atomic proposition on left side
• B. Single or multiple atomic proposition on left side
• C. A single atomic proposition on left side and a single atomic proposition on right side
• D. A single atomic proposition on left side or an empty left side

Answer 1

Ans D

In a Horn clause Left side can be single atomic proposition or empty.

Eg1 : loves(sh!va, gateoverflow) -> loves (sh!va, knowledge) ^ gives(gateoverflow,knowledge) // means shiva lives knowledge and gateoverflow gives knowledge. It implies shiva loves gateoverflow. Here LHS is single atomic clause.

Eg2: power( knowledge) // means knowledge is power. LHS is empty

Answer 2

Ans is D 

A single atomic proposition on left side or an empty left side

Horn clause it is a  disjunction of literals of which at most one is positive  (zero or one)

A Horn clause is a clause containing at most one positive literal. A definite clause contains exactly one positive literal. Examples of a Horn Clause [¬Child, ¬Mail, Boy] Not a Horn Clause [Rain, Sleet, Snow]