  The combination of nondeterminism and probability in concurrent systems lead
to the development of several interpretations of process behavior. If we
restrict our attention to linear properties only, we can identify three main
approaches to trace and testing semantics: the trace distributions, the
trace-by-trace and the extremal probabilities approaches. In this paper, we
propose novel notions of behavioral metrics that are based on the three classic
approaches above, and that can be used to measure the disparities in the linear
behavior of processes wrt trace and testing semantics. We study the properties
of these metrics, like non-expansiveness, and we compare their expressive
powers.
