Definability in Regular Time Theories

In order to develop a flexible and powerful programming theory an appropriate formal theory is required which permits us to define all the objects and notions necessary for the theoretical characterization of programs and programming languages in a uniform way. The required formal theory can be ensured by an appropriate definition theory which allows the effective usage of fixed-point equations. Effectivity means that the equations can be solved in finitely many steps. Moreover, in programming theory it is important to work with explicitly defined notions and objects. Therefore we expect that the implicit definitions given in the form of fixed-point equations can be turned into explicit ones. Thus arises the requirement that the solutions of fixed-point equations should be definable.