Sommerville-Software-Engineering-10ed

594 Chapter 20 ■ Systems of systems
Systems
knowledge
System
selection
Conceptual
design
Interface
development
Integration and
deployment
Architectural
design
Figure 20.6 An SoS
engineering process
Governance and management policy setting
The problems of software SoS engineering have much in common with the problems
of integrating large-scale application systems that I discussed in Chapter 15
(Boehm and Abts 1999). To recap, these were:
1. Lack of control over system functionality and performance.
2. Differing and incompatible assumptions made by the developers of the different
systems.
3. Different evolution strategies and timetables for the different systems.
4. Lack of support from system owners when problems arise.
Much of the effort in building systems of software systems comes from addressing
these problems. It involves deciding on the system architecture, developing software
interfaces that reconcile differences between the participating systems, and
making the system resilient to unforeseen changes that may occur.
Software systems of systems are large and complex entities, and the processes
used for their development vary widely depending on the type of systems involved,
the application domain, and the needs of the organizations involved in developing
the SoS. However, as shown in Figure 20.6, five general activities are involved in
SoS development processes:
1. Conceptual design I introduced the idea of conceptual design in Chapter 19, which
covers systems engineering. Conceptual design is the activity of creating a highlevel
vision for a system, defining essential requirements, and identifying constraints
on the overall system. In SoS engineering, an important input to the conceptual
design process is knowledge of the existing systems that may participate in the SoS.
2. System selection During this activity, a set of systems for inclusion in the SoS
is chosen. This process is comparable to the process of choosing application