Abstract: Techniques for requirements definition using interactive prototyping are described, including receiving an input from a client, wherein the client is installed on a first computer in data communication with an application simulation server implemented on a second computer, the input being manipulated to graphically identify a requirement for an application being generated using the first computer and the second computer, evaluating the input to identify executable program code associated with the requirement, transforming the input into the executable program code, wherein the application is designed by providing input at the first computer and simulated using the executable program code on the second computer, and generating an interactive simulation of the application by running the executable program code in a simulation environment on the second computer and displaying the application on the first computer, including one or more interfaces associated with the application.