Business enterprises operate as components of what is commonly referred to as a system of innovation. The system of innovation is the context for a process of innovation that can be described in terms of the knowledge sources and flows that lead to commercial advances. In this paper, we develop a model of the innovation process and of the system of innovation in which it takes place. The model, which describes the system from the perspective of the firm or enterprise, has the following properties: (a) it is flexible in its application but symmetrical in structure, making it easier to generalize or specialize; (b) it is simple, which helps makers and implementers of policy to visualize their role in the system; and (c) it is quantifiable, which aids comparisons among firms and among different systems of innovation. We make some applications of the new model, and show how other frameworks can be mapped onto it. In particular, we show the relationship with the European Community's model Innovation Survey and based on that, make some comments on future directions for survey instruments.