  There has been significant interest of late in generating behavior of agents
that is interpretable to the human (observer) in the loop. However, the work in
this area has typically lacked coherence on the topic, with proposed solutions
for "explicable", "legible", "predictable" and "transparent" planning with
overlapping, and sometimes conflicting, semantics all aimed at some notion of
understanding what intentions the observer will ascribe to an agent by
observing its behavior. This is also true for the recent works on "security"
and "privacy" of plans which are also trying to answer the same question, but
from the opposite point of view -- i.e. when the agent is trying to hide
instead of revealing its intentions. This paper attempts to provide a workable
taxonomy of relevant concepts in this exciting and emerging field of inquiry.
