1. An apparatus comprising: a shared database organized around a common schema, the shared database being shared by multiple users having access to different subsets of the data in the shared database; a first application to provide access to the shared database using the common schema, the first application having a first schema extension having a first set of additional objects, the first set of additional objects being defined by the first application; and a second application to provide access to the shared database using the common schema, the second application having a second schema extension having a second set of additional objects, the second set of additional objects being defined by the second application, wherein the first and second applications present views of and operations on the shared database that are extended by the respective schema extension.