Plotkin used the models of reduction in order to obtain a semantic characterization of static type inference in the pure -calculus. Here we apply these models to the study of a nondeterministic language, obtaining results analogous to Plotkin's. 1 Introduction The models of reduction are a generalization of the usual syntactic -models for the pure -calculus (see [Plo92] and the references therein). If a term M reduces to a term N then its interpretation in a model of reduction is "smaller than" or equal to the interpretation of N (and not necessarily equal as in -models). Plotkin obtained a series of soundness and completeness results for static type inference with respect to models of reduction. With type inference in mind, it seems natural that M and N be interpreted differently, since it may be possible to infer a type for N but not for M . The study of nondeterministic languages gives rise to an alternative motivation for considering models of reduction. In nondeterministic lang...