Onoin Structure of OA Framework

OA Framework applications can be abstracted into a series of concentric layers, like an onion. The core layer represents the database and the surface layer represents the application pages. In between is a number of business logic and user interface layers. This layering allows for generic code and components to be implemented at the inner layers to maximize their reuse across the outer layers. For example, attribute validation is implemented at the Entity Object (a BC4J object-oriented representation of a database table in the middle tier) level. All application pages that provide the user with the ability to populate or update the value of the subject attribute would receive attribute validation for free through the underlying entity object. On the user-interface side, reusable components can be saved as shared regions in the metadata services (MDS) repository and reused across several pages. An administrator can choose to personalize the shared region such that the personalization impacts all instances of the same region across pages or personalize the shared region only in the context of the current page