158 WebSphere Version 5 Application Development Handbook
Moving from analysis to design
In object-oriented analysis and design, we typically need two different
perspectives of the system:
Analysis model, which is an implementation-independent view
Design model, which is an implementation-dependent view
The analysis model focuses on what the system will do, while the design model
focuses on how the system will do it.
The design model represents the PiggyBank application components and
determines their appropriate placement and use within the overall architecture.
The design model is based on the analysis and architectural requirements. Refer
to “Analysis” on page 119 and “Architecture” on page 143.
Design model structure
The PiggyBank design model partitioning strategy follows the application
architecture, whereas the design layer packages represent the different
application layers. Each layer has a specific responsibility. The design layer
packages are derived from the application architecture described in “Application
architecture” on page 146.
Figure 8-1 shows the specified design layer packages for the PiggyBank
application design model.
In addition to the design model layers derived from the application architecture,
we introduce an additional layer named Common Elements. The Common
Elements << layer >> captures the design model components that are shared
across the other design layers.