4. A computer-readable storage medium storing program code, the program code comprising: code to call a constructor to register an interface to a description of a persistent class; code to access the registered interface to determine an internal structure of the persistent class; code to process an instance of the persistent class based on the determined internal structure, wherein the instance of the persistent class is a persistent database object; code to determine, based on the determined internal structure, members of the persistent database object that are filled with default values; code to store the persistent database object in a database; code to reduce storage demands on the database by removing the default values from the persistent database object before the storing of the persistent database object in the database; code to read the persistent database object from the database after the storing of the persistent database object in the database; code to populate the determined members of the persistent database object with the default values after the reading of the persistent database object from the database; code to define an index associated with one or more members of the instance based on the determined internal structure; and code to verify referential integrity of the instance.
4. A computer-readable storage medium storing program code, the program code comprising: code to call a constructor to register an interface to a description of a persistent class; code to access the registered interface to determine an internal structure of the persistent class; code to process an instance of the persistent class based on the determined internal structure, wherein the instance of the persistent class is a persistent database object; code to determine, based on the determined internal structure, members of the persistent database object that are filled with default values; code to store the persistent database object in a database; code to reduce storage demands on the database by removing the default values from the persistent database object before the storing of the persistent database object in the database; code to read the persistent database object from the database after the storing of the persistent database object in the database; code to populate the determined members of the persistent database object with the default values after the reading of the persistent database object from the database; code to define an index associated with one or more members of the instance based on the determined internal structure; and code to verify referential integrity of the instance. 6. The medium according to claim 4 , the program code further comprising: code to define a key associated with one or more members of the instance based on the determined internal structure.