The purpose of implementation is:

• define the organization of the code, in terms of implementation subsystems organized in layers
• implement the design elements in terms of implementation elements (source files, binaries, executable programs, and others)
• test the developed components as units
• integrate the results produced by individual implementers (or teams), into an executable system

The Implementation discipline limits its scope to how individual classes are to be unit tested. System test and integration test are described in the Test discipline.

The implementation is related to other disciplines:

• The Requirements discipline describes how to, in a use-case model, capture requirements that the implementation should fulfill.
• The Analysis & Design discipline describes how to develop a design model. The design model represents the intent of the implementation, and is the primary input to the Implementation discipline.
• The Test discipline describes how to integration test each build during the integration of the system. It also describes how to test the system to verify that all requirements have been met, as well as how defects are detected and submitted.
• The Environment discipline describes how to develop and maintain supporting artifacts that are used during implementation, such as the process description, the design guidelines, and the programming guidelines. 
• The  Deployment discipline describes how to use the implementation model to produce and deliver the code to the end-customer.
• The Project Management discipline describes how to best plan the project. Important aspects of the planning process are the iteration plan, change management and defect tracking systems.