  The behavior of a cyber-physical system (CPS) is usually defined in terms of
the input and output signals processed by sensors and actuators. Requirements
specifications of CPSs are typically expressed using signal-based temporal
properties. Expressing such requirements is challenging, because of (1) the
many features that can be used to characterize a signal behavior; (2) the broad
variation in expressiveness of the specification languages (i.e., temporal
logics) used for defining signal-based temporal properties. Thus, system and
software engineers need effective guidance on selecting appropriate signal
behavior types and an adequate specification language, based on the type of
requirements they have to define. In this paper, we present a taxonomy of the
various types of signal-based properties and provide, for each type, a
comprehensive and detailed description as well as a formalization in a temporal
logic. Furthermore, we review the expressiveness of state-of-the-art
signal-based temporal logics in terms of the property types identified in the
taxonomy. Moreover, we report on the application of our taxonomy to classify
the requirements specifications of an industrial case study in the aerospace
domain, in order to assess the feasibility of using the property types included
in our taxonomy and the completeness of the latter.
