If several implementers work (as a team) on the same Implementation Subsystem, the changes from the individual implementers need to be integrated to create a new consistent version of the Implementation Subsystem. The integration results in series of builds in a subsystem integration workspace. Each build is then integration tested by a tester or an implementer executing the developer tests. Following testing, the Implementation Subsystem is delivered into the system integration workspace.

Integration is typically carried out by a single person (for a small project on which the build process in simple) or a small team (for a large project on which the build process is complex). The integrators need experience in software build management, configuration management, and experience in the programming language in which the components to be integrated are written. Because integration often involves a high degree of automation, expertise in operating system shell or scripting languages and tools like 'make' (on Unix) or 'ant' (for Java) is also essential.