This paper focuses on the task of design verification using both knowledge of the structure of a device and its intended functions. In particular, it addresses the question of when one can say a behavior predicted by a prediction system achieves the desired function in the manner intended by the designer. We use Functional Representation to represent the function of device and the expected causal mechanism for achieving it. We present a formal definition of matching between a system trajectory generated by a simulation system and the description of a causal process to achieve a function expressed in Functional Representation. We believe that evaluating a behavior with respect to the expected causal process as well as the function improves the chances of uncovering hidden flaws in a design that may otherwise go undetected at an early stage.