  Network systems and their control are highly important and appear in a
variety of applications, including vehicle platooning and formation con- trol.
Especially vehicle platoons are highly investigated and an interesting problem
that arises in this area is string stability, which broadly spoken means that a
input signal amplifies unbounded as it travels through the vehicle string.
However, various definitions are commonly used. In this paper, we aim to
formalise the notion of string stability and illustrate the importance of those
distinctions on simulation examples. A second goal is to generalise the found
definitions for general network systems.
