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. In this paper, 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.