The concept is specific to temporal databases (+R1) and is well defined and understood in the real world (+R2, +R3). It has been used and referred to in many works (+R4). The name is intuitive (+E8), it is not as widely used as ``history'' (-E3), but it describes the concept more accurately (+E9) than ``history,'' i.e., the common use of history is in reference to the past, but a temporal database can have a time sequence that involves future times.