Time-Oriented Data Model

A minimal extension of relational data model for logical modeling of the category of time in databases is offered. The time is considered as a totally ordered set. In the frame of suggested datamodel the homogeneous model of representation of time in relations is adopted. Allowing the homogeneity, the modeling of the temporal aspect of databases is achieved by means of two temporal attributes. The temporal attribute is considered as abstract data type. A formal definition of temporal relation which is based on abstraction of generalization is given. The semantics of operators update and delete is changed. A temporal algebra and calculus are developed. Also new aggregate functions are suggested considering the time aspect of the object behavior in the given enterprise. In order to give temporal integrity constrains closed formulas are used. The problems of partial support of evolution of the database schemes are considered.