This chapter deals with the analysis of problems that involve differential constraints. One fundamental result is the Frobenius theorem, which allows one to determine whether the state transition equation represents a system is actually nonholonomic. In some cases, it may be possible to integrate the state transition equation, resulting in a problem that can be described without differential models. Another result is Chow's theorem, which indicates whether a system is controllable. Intuitively, this means that the differential constraints can be completely overcome by generating arbitrarily short maneuvers. The car-like robot enjoys the controllability property, which enables it to move itself sideways by performing parallel parking maneuvers.