Temporal knowledge bases

Traditionally a database represents a `snap-shot´ of the world. When events occur and values change, the database is `updated´ to reflect these changes and the previous version is overwritten. However, this practice has a number of drawbacks which are listed. The advent of high density, low cost optical disc stores has made it possible, in certain applications, to adopt the idea that no data should ever be deleted. Under this regime, when new data supersedes old, it is merely added to the accumulating store of data (with some cross reference to the `previous version´). It is then possible to access the complete historical record of every datum. The `write-once-read-mostly´ (WORM) optical disc is the most appropriate for an information store of this kind. The advantages of such a system time-stamps, temporal data organization and dealing with rules are discussed