Chapter 8: Physical Design

Overview

Following the conceptual and logical design stages, the third and final stage of the application design process is physical design. The purpose of physical design is to apply technical constraints and decisions on the logical components created during logical design. Physical design also usually involves designing internal data structures, record formats, and a data dictionary.

Whereas the conceptual and logical stages were approached from the perspective of the underlying business (making sure every business requirement was fulfilled), the physical design stage should be approached from the perspective of the developer (fulfilling the technical requirements). At the end of this stage, we will have created a technical specification or blueprint that will lead us right into the development phase. The technical specification will contain details regarding the target platform or set of technologies—any technical issues will be resolved by the end of this phase.

The physical design stage can be broken down into five smaller tasks:

• Deriving the physical design from the logical design

• Developing an appropriate deployment model

• Creating the physical design for maintenance

• Creating the physical data model

• Validating the physical design

This chapter discusses these five steps in greater detail.