A method and computer program product for building a multiple layer object-oriented software application with reusable components. The method includes creating business classes containing a business logic for the software application, wherein the business classes are organized into hierarchies identified as namespaces, and then generating executable programming code for the software application. From there, the method may include placing the executable programming code into an at least one assembly structure for an associated layer, wherein a security token is required to access the business classes, and wherein the business classes are created to validate each security token passed by a user interface.