Applying aspect-oriented programming for instance adaptation in object-oriented databases

Developing object-oriented database for web applications may not remain constant and may vary to a large extent due to a variety of reasons like correcting mistakes, adding new features or any changes in the structure of the real world artifacts modeled in the database. Class versioning is one of the evolution strategy employed that addressing the above issues. The existing strategy for instance adaptation introduces the adaptation code directly into the class versions upon evolution, Consequently, if the behavior of a routine needs to be changed and maintenance has to be performed on all the class versions it was introduced. A new approach for instance adaptation is achieved by encapsulating the instance adaptation code through aspects - abstractions introduced by aspect-oriented programming that localize cross-cutting concerns. A web-based student database system was developed with different versions and the versioning problem was solved using update/backdate aspects with selective lazy conversion. The update/backdate aspects are invoked whenever version incompatibility arises and selective lazy conversion aspect is invoked when the condition for converting objects into new version is satisfied and this converts only a subset of the old version objects into new version.