Once the data objects and the set of actions required for each object have been defined, the application designer should determine the existence of any previously-created application object classes for that type of data object. The use of existing application objects, with additional actions and methods handled through subclassing, can significantly reduce the amount of coding required.
The accurate identification of existing application object classes requires that each application object, upon completing its final testing, must be placed in an object library, and its external interfaces (both input and output) must be fully documented and placed in a retrieval system from which the object's description may be recalled by designers of future applications. The organization and level of sophistication of such a system is largely at the discretion of the development organization, but becomes more crucial as the number of application objects grows larger over time. It is strongly recommended that any organization embarking on a strategy of object-oriented application development should adopt an efficient object library management system from the outset.