Providing Time-Related Constraints for Conventional Database Systems
Talib Hashim Abbod, Kelly Thomas Brown, Hugh Noble · 1987
A model for a historical database is described which is based upon time-stamped tuples as the unit of storage. The model includes both physical and logical time-stamps. The techni-cal characteristics of write-once laser discs prevent the use of double logical time-stamps. The model distinguishes version from correction-updates. It is shown that if set-valued attributes are involved the use of null values is unavoidable if back-dated correction-updates are allowed. A method of handling user-defined integrity constraint rules is outlined which involves the mainte-nance of a time-stamped trace of such rules.