When building applications to solve business problems, you must consider the business requirements driving application development. At any point in the design process, the current state of the design should be directly traceable to the business problem and requirements.
The four client/server design stages, conceptual, logical, physical, and future are used to create optimized database systems. These stages progress from simple to complex design in order to provide a database implementation that accommodates your needs.
Figure 6.6 The four design stages of creating a client/server database
Conceptual
During the conceptual design phase you should develop usage scenarios. These scenarios represent the user 's view of the solution to a specific business problem. A conceptual view places the emphasis on solving the business problem and deriving a solution that conforms to the needs and requirements of the users.
Logical
During logical design, you derive business objects and their related services directly from these usage scenarios. The logical view of the solution provides a basis for evaluating different physical options. It also formalizes the solution for the project team.Physical
Physical design maps business objects and services to physical components. The components should be directly traceable to the originating business objects and through them to the usage scenarios. The physical design also focuses on leveraging existing infrastructure and technologies to minimize risk and to shorten development cycles.Future
One or more usage scenarios for future (or proposed) extensions of the application or system are the foundation for all subsequent design activities. These usage scenarios embody the user's vision of the business solution and are as detailed as necessary to communicate this understanding. For each business activity, such as processing customer payments, a usage scenario will be developed. One scenario may describe how payments by check are processed, and another may describe how payments by credit card are processed .