Observable system

Definition

A system is called (completely) observable if for any initial $t_0$, any initial state $\mathbf{x}(t_0)$ can be determined from observation of the output $\underset{\sim}{\mathbf{y}}[t_0, t]$ over a finite time interval (i.e. $t$ is finite) when the input $\underset{\sim}{\mathbf{u}}[t_0, t]$ is known over the same interval.

#incomplete

References

1. P. E. Sarachik, Principles of Linear Systems, Cambridge Press, 1996, pp. 158-162.