Currently there is no easy or efficient way to have a debounce timer for a property's value. The way the debounce timer normally works is when a value, let's say temperature, rises up to the alert setpoint, it will start a timer. The timer is programmed for a certain amount of time, say 5 seconds. While the temperature value is at or above the alert setpoint, the timer keeps timing until it times out at 5 seconds. If the temperature bounces below the alert setpoint, the timer stops timing and resets back to 0. When the temperature reaches the setpoint again, the timer starts from the beginning. This way, the temperature must be at or above the setpoint for at least 5 seconds before generating an alert. Without a timer like this, it is possible to generate hundreds of alerts within several minutes.
Adding this as a programmatically configurable option in both the Alerts and in Subscriptions would allow for utilizing a debounce timer for both when alerting when outside the configured range and for a datachange event.