THERE IS NO FULLY ABSTRACT FIXPOINT SEMANTICS FOR NONDETERMINISTIC LANGUAGES WITH INFINITE COMPUTATIONS

It is well known that for many non-deterministic programming languages there is no continuous fully abstract fixpoint semantics. This is usu ally attributed to ''problems with continuity'', that is, the assumpti on that the semantic functions should be continuous supposedly plays a role in the difficulties of giving a fully abstract fixpoint semantic s. We show that for a large class of non-deterministic programming lan guages there is no fully abstract least fixpoint semantics even if one considers arbitrary functions (not necessarily continuous) over arbit rary partial orders (not necessarily complete).