Migrating non-persistent objects when one or more of the superclass fields of the object are modified

摘要

This Object-Oriented programming system migrates persistent objects when their class declarations are modified. The objects and their class descriptions are persistently stored and the persistent versions of an objects' superclass descriptions are compared to later versions of the objects' superclass descriptions. When a persistent version and a later version of the class description for the object differ, the object is migrated from the persistent version to the later version based on the differences between the two superclass descriptions. Finally, the migrated object is persistently stored with changes in its persistent class description.