We identify an emerging class of software application as “complex” systems. They are complex in that they must adapt to a changing environment. This motivates us to revisit the “Control Paradigm” for software architecture. In this paper, we go beyond that approach and introduce the concept of viability as the overall characteristic of the behavior desired in such systems.We present architecture to guide in software engineering of this class of complex system. The architecture is based on a Cybernetic model called the Viable System Model. As an application of the approach, we are developing a Smart Lecture Room. We report on our first efforts in employing the architecture to develop this application.