Temporal databases – Specialised databases series – Part 4

For the penultimate part of the specialised database series we look at Temporal databases ( (Part 1Part 2, Part 3)

Temporal databases are concerned with storing data relating to time instances. It provides temporal data times and stores data relating to past, present and future time. There are a number of examples of applications where temporal database technology is used. Financial applications such as; FX trading platforms, accounts and banking and also scheduling applications such as; hotel reservations, project management and train schedules. (Jensen, 2000)

A temporal database is an ordered sequence of time duration points set by the application known as chronon. Chronon describe the minimal granularity this maybe be 1 millisecond, 1 second or 1 minute, whichever the application chooses. However choosing a minimum granularity can lead to events occurring within the same period, they would then be considered simultaneous events when this may not be the case.

There are two common aspects that are associated in the temporal database; they are referred to as time dimensions (Wikipedia, 2011) (Elmasri & Navathe, 2003):

  • Valid time – A time period in which a fact is true or false in the “mini-world”, a database representation of the real world. A temporal database using this is called a valid time database.
  • Transaction time – A time period when the fact is stored in the database. The fact is rarely deleted, as it may need to be used for auditing purposes but is considered to be invalid. A temporal database using this is called a transaction time database.

Applications can decide to make use of either type or a combination of both known as a bitemporal database. If neither of these options proves to be appropriate for the application a custom user defined solution can be created and is called a user-defined time database.

That’s it for part 4, until next week….

Thanks,

Sara :)

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If you can’t wait for the series here is the full text.

References

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