tive literals true in all Herbrand(Lp) models is the same as the set of positive
literals true in all models of comp(P), which is recursively enumerable.)
There is a very neat fixpoint characterization of the Herbrand models of
comp(P) in terms of the operator T
p
defined in section 5:
THEOREM 14
The Herbrand models of comp(P) are the fixpoints of T
p
.
Proof:
Note that the result is true whatever language is used for Ρ and
comp(P). This is almost obvious in view of our remark above in the section on
fixpoint models that an interpretation I is a fixpoint of T
p
iff it is a supported
model of P, since "supported" is equivalent to
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