I know the environment of an intelligent agent is divided to discrete and continuous. But I think they are relevant to sensors and actuators of the agent itself. Moreover, environment may have many mutable factors,(some continuous, some discrete). For example for an agent which is an expert system (computer program) to play the role of a physician, what is the environment, is it continuous or discrete?Please give some examples of continuous environments. 
What is a continuous environment for an agent?
artificial intelligence