Discussion


``History'' is a general concept, intended in the sense of ``train of events connected with a person or thing''. Although it usually has to do with past events (-E5), its use for the future—as introduced by prophecies, science fiction, scientific forecasts—does not seem to present comprehension difficulties (there are much more problems with the adjective ``historical''). Talking about future history, requires the same extension of meaning as required by talking about future data.

In the realm of temporal databases, the concept of history is intended to include multiple time dimensions as well as the data models (+R1). Thus we can have valid-time histories, transaction-time histories, bitemporal histories, user-defined histories, etc. However, multi-dimensional histories can be defined from mono-dimensional ones (e.g. a bitemporal history can be seen as the transaction-time history of a valid-time history).

Formally or informally, the term ``history'' has been often used in many temporal database papers (+R4), also to explain other terms. For instance, salary history, object history, transaction history are all expressions used in this respect.

The alternative term ``temporal value'' is less general, since it applies when ``history'' specializes into attribute history (value history). Moreover, ``history'' is a slightly more general concept than ``time sequence'': differnet time sequences (with different time granularities) could be extracted from the same history. Therefore the definition of ``history'' does not prevent defining ``time sequence.''

``History'' is also preferred over alternative names because it allows a better definition of related terms. Since it implies the idea of time, ``history'' does not require futher qualifications as ``sequence'' or ``series'' do (+E2). In particular, ``history'' well lends itself to be used as modifier (+E1), even though ``time sequence'' is an alternative consolidated term (-E3,-E6).

``History'' is natural (+E8) and precise (+E9), whereas ``temporal value'' may recall a temporal element (e.g. timestamp value) and ``time sequence'' may recall a sequence of temporal elements.