Toward a multihomogeheous model for a temporal database

In a conventional database, out of date information is deleted from time to time to keep the database up-to-date. In some applications it is not appropriate to discard old information. In a temporal database, time values are associated with each data item to indicate its period of validity. We propose a model for temporal databases within the framework of classical relational database theory. Our basic model is homogeneous in the sense that the periods of validity of all the attributes in a given tuple of a temporal relation are identical. The model is realized as a temporal parameterization of static relations. The concepts of normal forms, dependencies, etc., can be extended to our model, allowing the proper initial structuring of the database. We develop relational algebra and tuple calculus for our model and prove their equivalence. We generalize the homogeneous model to a multihomogeneous model which allows us to model a significant part of the real world.