1. A method, in a data processing system, for modeling an asynchronous interface, comprising: identifying logic of the asynchronous interface in an integrated circuit design; converting the logic of the asynchronous interface into primitive logic elements; replacing, by the data processing system, the primitive logic elements with corresponding expanded primitive logic elements, wherein the expanded primitive logic elements each comprise an additional deterministic input and an additional deterministic output, wherein the additional deterministic input is representative of whether a corresponding data input to the expanded primitive logic element is deterministic or non-deterministic, and wherein the additional deterministic output is representative of whether a corresponding data output of the expanded primitive logic element is deterministic or non-deterministic; running a simulation of the asynchronous interface using the expanded primitive logic elements to thereby model the asynchronous interface; and generating an output indicating results of running the simulation of the asynchronous interface using the expanded primitive logic elements to thereby model the asynchronous interface.