  In the last few years there has been a growing interest in the use of
symbolic models for the formal verification and control design of purely
continuous or hybrid systems. Symbolic models are abstract descriptions of
continuous systems where one symbol corresponds to an "aggregate" of continuous
states. In this paper we face the problem of deriving symbolic models for
nonlinear control systems affected by disturbances. The main contribution of
this paper is in proposing symbolic models that can be effectively constructed
and that approximate nonlinear control systems affected by disturbances in the
sense of alternating approximate bisimulation.
