|
A temporal database is a database with built-in support for handling data involving time, being related to the slowly changing dimension concept, for example a temporal data model and a temporal version of Structured Query Language (SQL). More specifically the temporal aspects usually include valid time and transaction time. These attributes can be combined to form bitemporal data. * Valid time is the time period during which a fact is true with respect to the real world. * Transaction time is the time period during which a fact stored in the database is considered to be true. * Bitemporal data combines both Valid and Transaction Time. It is possible to have timelines other than Valid Time and Transaction Time, such as Decision Time, in the database. In that case the database is called a multitemporal database as opposed to a bitemporal database. However, this approach introduces additional complexities such as dealing with the validity of (foreign) keys. Temporal databases are in contrast to current databases, which store only facts which are believed to be true at the current time. ==Features== Temporal databases support managing and accessing temporal data by providing one or more of the following features:〔〔 * A time period datatype, including the ability to represent time periods with no end (infinity or forever) * The ability to define valid and transaction time period attributes and bitemporal relations * System-maintained transaction time * Temporal primary keys, including non-overlapping period constraints * Temporal constraints, including non-overlapping uniqueness and referential integrity * Update and deletion of temporal records with automatic splitting and coalescing of time periods * Temporal queries at current time, time points in the past or future, or over durations * Predicates for querying time periods, often based on Allen’s interval relations 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「temporal database」の詳細全文を読む スポンサード リンク
|