Object histories as a foundation for an active OODB

Several links exist between active and temporal databases. These are summarised by the observation that rules are triggered by a specified evolution of the database. We discuss the relation between active and temporal database using DEGAS, an object based active database programming language. To achieve full active database functionality, a DEGAS object records its complete history. Hence, all data needed for a temporal database supporting a single temporal dimension is provided. Furthermore, the semantics of the active behaviour of DEGAS are defined straightforwardly in terms of the object history. Finally we discuss the advantages and disadvantages of extending DEGAS with a second time dimension (to achieve full temporal functionality) from an active database perspective.