 An interesting difference between temporal logic on the one hand, and dynamic logic and Hoare logic on the other, is that the former is what in the literature is called an endogenous logic, while the latter are so-called exogenous logics. A logic is exogenous if programs are explicit in the logical language, while for endogenous logics this is not the case. In an endogenous logic such as temporal logic the program is assumed to be fixed, and is considered part of the structure over which the logic is interpreted (Harel et al. 2000, 157). Exogenous logics are compositional and have the advantage of allowing analysis by structural induction. Later Pratt (1979b) tried to blend temporal and dynamic logic into what he called process logic, which is an exogenous logic for reasoning about temporal behavior. 