1. A method in a computer-aided design system for generating a functional design model of a negative unknown Boolean state, said method comprising: generating a functional computer-simulated representation of initializing one or more initial simulated logic elements to an unknown Boolean state; generating a functional computer-simulated representation of feeding the unknown Boolean state to one or more first simulated logic elements; generating a functional computer-simulated representation of simulating one or more first results resulting from the first simulated logic elements, the first results including at least one negative unknown Boolean state, wherein the negative unknown Boolean state is the opposite of the unknown Boolean state; generating a functional computer-simulated representation of feeding the negative unknown Boolean state to one or more second simulated logic elements; and generating a functional computer-simulated representation of simulating one or more second results resulting from the second simulated logic elements.