  Unlike traditional cameras, event cameras measure changes in light intensity
and report differences. This paper examines the conditions necessary for other
traditional sensors to admit eventified versions that provide adequate
information despite outputting only changes. The requirements depend upon the
regularity of the signal space, which we show may depend on several factors
including structure arising from the interplay of the robot and its
environment, the input-output computation needed to achieve its task, as well
as the specific mode of access (synchronous, asynchronous, polled, triggered).
Further, there are additional properties of stability (or non-oscillatory
behavior) that can be desirable for a system to possess and that we show are
also closely related to the preceding notions. This paper contributes theory
and algorithms (plus a hardness result) that addresses these considerations
while developing several elementary robot examples along the way.
