Abstract
We consider that nondeterministic programs behave as badly as they can and loop forever whenever they have the possibility to do so. This is the demonic approach of nondeterministic programs. We deal with a relational algebra model to define a refinement fuzzy ordering (demonic fuzzy inclusion) and also the associated fuzzy operations which are fuzzy demonic join (coproduct(fuz)), fuzzy demonic meet (Pi(fuz)) and fuzzy demonic composition (Pi(fuz)). We give also some properties of these operations and illustrate them with simple examples. Our formalism is the relational algebra.