A representation method of time-varying characteristics of entity on the basis of core-surface concept

Until today, techniques for modeling and managing the time varying characteristics of entities in database have been proposed. These techniques are mainly classified into two categories: time stamp method and version method. These methods limit the representation/manipulation capabilities because the change of class membership for an object is not well specified and the transitional states must be related mutually along the system defined time axis. We propose a method which is basically derived from the object oriented paradigm, for modeling time varying characteristics of entities so as to be free from the above two limitations in the traditional methods. We introduce two representation media: core and surface. The core represents invariant features of entity, while the surface denotes variant features of entity. A snapshot of an entity is represented as an aspect, which is a database instance composed of the core and surfaces.