Flexible Scheme Evolution in Relational Database Model
-
Specification In a typical database management system a concept of database schema provides full information about a logical organization of database structures. The principal requirement of logical database consistency states that in every moment of time contents of a database must be consistent with the respective database schema. The queries submitted to a database must be syntactically consistent with a database schema as well. The idea of scheme evolution refers to the changes in a database scheme over a certain period of time. It would be convenient to modify a database schema depending on users' requirements. The conventional query languages, like for instance SQL, does not allow for references to a number of different versions of the same database schema. Unfortunately, the frequent modifications of database schema require restructuring of database contents and modification of user applications. As the result, frequent evolution of a database schema significantly decreases performance of a database system and requires continuous upgrades of user applications. Objectives The objective of this project is to propose architecture for database system where frequent evolution of database scheme has no significant impact on performance of the system and it is transparent to users' applications.