During analysis modeling, the problem is analyzed by breaking it down and studying it on a use case–by–use case basis. During design modeling, the solution is synthesized by designing a software architecture that defines the structural and behavioral properties of the software system. To successfully manage the inherent complexity of a large-scale software system, it is necessary to provide an approach for decomposing the system into subsystems and developing the overall software architecture of the system. After performing this decomposition, each subsystem can then be designed independently, as described in subsequent chapters.

Section 13.1 describes issues in software architectural design. To design the software architecture, it is necessary to start with the analysis model. Several decisions need to be made in designing the software architecture:

• Integrate the use case–based interaction models into an initial software architecture, as described in Section 13.2.

• Determine the subsystems using separation of concerns and subsystem structuring criteria, as described in Sections 13.3 and 13.4, respectively.

• Determine the precise type of message communication among the subsystems, as described in Section 13.5.

ISSUES IN SOFTWARE ARCHITECTURAL DESIGN

In the analysis of the problem domain and structuring a system into subsystems, the emphasis is on functional decomposition, such that each subsystem addresses a distinctly separate part of the system (as discussed in Section 13.3). The design goal is for each subsystem to perform a major function that is relatively independent of the functionality provided by other subsystems.