Software Architecture: Foundations, Theory, and Practice

Chapter 10. Deployment and Mobility

After a software system has been designed, implemented, and validated, it is ready for operation. That usually requires that the system's components and connectors first be distributed to the "target" hardware processors. A software system cannot fulfill its purpose until it is deployed, that is, until its executable modules are physically placed on the hardware devices on which they are supposed to run. The outcome of the activity of placing a system's software components on its hardware hosts is the deployment of the system's architecture.

Once the system is in operation, it is possible, and often necessary, to change the physical location of its hardware hosts. For example, laptop computers, personal digital assistants (PDAs), cellular telephones, software-controlled radios, and computers embedded in a vehicle, all move regularly while staying connected. More challenging, more interesting to a software engineer (and even a user), and more pertinent to this book is the relocation or migration of a software component or connector from one hardware host to another. This may need to be done to improve the system's performance, perhaps by collocating a processing component with the data it needs, lessen the computational load on a given host, or to achieve some other property. Relocating software modules in this manner changes the deployment view of the software system's architecture during the system's run time, and is referred to as migration