 In basic logic programs \(\tau\) is a logical atom and \(\phi_1, \dotsc, \phi_n, \psi_1, \dotsc, \psi_m\) are logical literals (i.e., atoms or negated atoms). The logical form or rules in such programs have been generalized in various ways (e.g.,  Alferes et al. 1995)  and many ways of interpreting rules have been proposed. To understand the meaning of the default negation not we consider a concrete example for a rule, namely: 