Representing retroactive and proactive versions in bi-temporal databases (2TDB)

Bi temporal databases allow users to record retroactive (past) and proactive (future planned) versions of an entity, and to retrieve the appropriate versions for bi temporal queries that involve both valid time and transaction time. Currently used timestamp representations are mainly for either valid time or transaction time databases. We first categorize the types of problems that can occur in existing models. These are: ambiguity; priority specification; and lost information. We then propose a 2TDB model that allows both retroactive and proactive versions, overcomes the identified problems, and permits the correction of recorded facts.