Analyzing and Securing Social Networks

65Cloud Computing and Semantic Web Technologies

body at most once and do not occur in the head are called unbound variables; all other variables are

called bound variables.

The proposed rules are of the form of an implication between an antecedent (body) and

a consequent (head). The intended meaning can be read as follows: whenever the condi-

tions specied in the antecedent hold, the conditions specied in the consequent must also

hold. Both the antecedent (body) and consequent (head) consist of zero or more atoms. An

empty antecedent is treated as trivially true (i.e., satised by every interpretation), so the

consequent must also be satised by every interpretation. An empty consequent is treated

as trivially false (i.e., not satised ...