Snapshot, Valid- and Transaction-time, and Bitemporal as Modifiers

The definitions of how ``snapshot,'' ``valid-time,'' ``transaction-time,'' and ``bitemporal'' apply to relations provide the basis for applying these modifiers to a range of other concepts. Let x be one of snapshot, valid-time, transaction-time, and bitemporal. Twenty derived concepts are defined as follows (+E1).

relational database

An x relational database contains one or more x relations.

relational algebra

An x relational algebra has relations of type x as basic objects.

relational query language

An x relational query language manipulates any possible x relation. Had we used ``some'' instead of ``any'' in this definition, the defined concept would be very imprecise (-E9).

data model

An x data model has an x query language and supports the specification of constraints on any x relation.

DBMS

An x DBMS supports an x data model.

The two model-independent terms, data model and DBMS, may be replaced by more specific terms. For example, ``data model'' may be replaced by ``relational data model'' in ``bitemporal data model.''

The nouns that have been modified above are not specific to temporal databases. Nouns specific to temporal databases, such as instant, chronon, interval, element, and span, may be modified by ``valid-time,'' ``transaction-time,'' and ``bitemporal.''