
Chapter
4
On the Declarative Semantics of Logic
Programs with Negation
Vladimir Lifschitz
Computer Science Department
Stanford University, Stanford,
CA
Abstract
A logic program can be viewed as a set of predicate formulas, and its declara-
tive meaning can be defined by specifying a certain Herbrand model of that
set. For programs without negation, this model is defined either as the
Herbrand model with the minimal set of positive ground atoms, or, equiv-
alently, as the minimal fixed point of a certain operator associated with the
program (van Emden and Kowalski). These solutions do not apply to general
logic programs, because a program wit