Abstract: The era of a world connected by networks, especially by Internet, has imposed new challenges to control theories and applications, and in the same time, provided new opportunities for their research and development. As a first step, this paper addresses some basic issues in network-based direct control systems and corresponding modeling and analysis. These problems are obvious and may not be important or fundamental in many situations, however, the purpose here is to initiate a discussion and call for effort along this direction by more experts in control and automation, so that a complete and scientific theory for network-based control systems can be established soon.