A cognitive engine (CE) is an intelligent package that turns the knobs and reads the meters of a controllable radio system. As discussed in Chapter 1, this concept was initially introduced as a software entity that interacts with an electronically configurable radio transceiver [1]. Early examples exhibited limited functionality and software portability, often focusing on fairly specific problems or approaches that were very dependent on particular aspects of the support platform. Subsequent work on the topic has developed many of the trends pioneered by these early examples and expanded the domain of a CE. However, it is important to consider that not much more than a decade has passed since the inception of the concept of a CE for radio application; there are a great many challenges left unsolved and capabilities left undiscovered. In fact, the full scope of CE is only beginning to develop and there is a vast territory left to explore.