Object evolution mechanisms in object databases:: Requirements, optional features and comparison

Nowadays, most Object Oriented Database Systems (OODBs) display serious shortcoming in their ability to model the evolving and multifaceted nature of common real world entities. While researcher in knowledge representation systems have been aware of this problem for some time, database systems represent an environment in which this problem is particularly severe. OODBs store objects over longer periods, during which the represented entities evolve. The intimate and permanent binding of an object to a single type (class) inhibits the tracking of real-world entities over time. In recent years, various mechanisms for supporting many-faceted and evolving objects in the context of OO data models have been proposed in the literature. This paper examines in a First part the semantics associated with object evolution and explores the implications of these semantics on object oriented concepts. In a second part, we discusses features regarding the functionality's of various object evolution mechanisms proposed in the literature in the context of OODBs and finally compares four representatives and more recent works in this area.