**Remark 30** (Resolution in PROLOG)**.** *In Example 45, we argued that Horn clauses in PROLOG should be rather considered as sketch implications than universally quantified implications.*

*Concerning* resolution*, there is also a discrepancy between the theoretical justification and the actual effect of the resolution procedure in PROLOG. Resolution is explained as a special case of the general principle of "proof by refutation" [40]. Actually, PROLOG computes, however, (in a constructive way!) a Horn clause that is semantically entailed by the Horn clauses and the facts in the given PROLOG program (compare the Semantic Deduction Theorem 2).*
