4DIS: A temporal framework for unifying meta-data and data evolution

Time is an important aspect of all real-woild pheiiümeria. Events occur at specilic points in time; objrcis and their rela-tionshiips exist and change over time. Tradii ionally, temporal database systems allow different snapsliots oi'data units to be modeled and queried. However, it has been quite difficult to model evolution of meta-data; this is primarily due to the lacli of proper logical data independence support in existing database systems. In this paper, we introduce a temporal object database model called Four Dimensional ïnjormation Space (4DIS). In 4DIS, both meta-data and data units are modeled uniformly as objects. The database is modeled as a set of relationships, each of which relates two individual objects. Each relation is also associated with a temporal dimension which supports valid and transaction time. This allows time to be naturally integrated with objects of arbitrary granularity and provides flexible logical data independence support for the database. Meia-data and data evolution could thus be unified in a standard framework. Temporal operations can also be evaluated against both meta-data and data units in a uniform manner.