  The behavior of a quantum system depends on how it is measured. How much of
what is observed comes from the structure of the quantum system itself and how
much from the observer's choice of measurement? We explore these questions by
analyzing the \emph{language diversity} of quantum finite-state generators. One
result is a new way to distinguish quantum devices from their classical
(stochastic) counterparts. While the diversity of languages generated by these
two computational classes is the same in the case of periodic processes,
quantum systems generally generate a wider range of languages than classical
systems.
