11gR2 : Edition Based Redinition.....Have multiple version of PL/SQL objects, views, synonyms in a single schema.....

Edition-based redefinition allows multiple versions of PL/SQL objects, views and synonyms in a single schema, which makes it possible to perform upgrades of database applications with zero down time

http://www.oracle-base.com/articles/11g/edition-based-redefinition-11gr2.php