  In this paper, we introduce two metrics, namely, age of actuation (AoA) and
age of actuated information (AoAI), within a discrete-time system model that
integrates data caching and energy harvesting (EH). AoA evaluates the
timeliness of actions irrespective of the age of the information, while AoAI
considers the freshness of the utilized data packet. We use Markov Chain
analysis to model the system's evolution. Furthermore, we employ
three-dimensional Markov Chain analysis to characterize the stationary
distributions for AoA and AoAI and calculate their average values. Our findings
from the analysis, validated by simulations, show that while AoAI consistently
decreases with increased data and energy packet arrival rates, AoA presents a
more complex behavior, with potential increases under conditions of limited
data or energy resources. These metrics go towards the semantics of information
and goal-oriented communications since they consider the timeliness of
utilizing the information to perform an action.
