  (2)  Program clauses are not necessarily well-founded. For example, the head of a clause may occur in its body. Well-founded programs are just a particular sort of programs. The use of arbitrary clauses without further requirements in logic programming is a motivation to pursue the same idea in proof-theoretic semantics, admitting just any sort of introduction rules and not just those of a special form, and in particular not necessarily ones which are well-founded. This carries the idea of definitional freedom, which is a cornerstone of logic programming, over to semantics, again widening the realm of application of proof-theoretic semantics.