The completion and approval of one or more deliverables characterizes a project phase. A deliverable is a measurable, verifiable work product such as a specification, feasibility study report, detailed design document, or working prototype. Some deliverables can correspond to the project management process, whereas others are the end products or components of the end products for which the project was conceived. The deliverables, and hence the phases, are part of a generally sequential process designed to ensure proper control of the project and to attain the desired product or service, which is the objective of the project.
In any specific project, for reasons of size, complexity, level of risk, and cash flow constraints, phases can be further subdivided into subphases. Each subphase is aligned with one or more specific deliverables for monitoring and control. The majority of these subphase deliverables are related to the primary phase deliverable, and the phases typically take their names from these phase deliverables: requirements, design, build, test, startup, turnover, and others, as appropriate.
A project phase is generally concluded with a review of the work accomplished and the deliverables to determine acceptance, whether extra work is still required, or whether the phase should be considered closed. A management review is often held to reach a decision to start the activities of the next phase without closing the current phase, for example, when the project manager chooses fast tracking as the course of action. Another example is when an information technology company chooses an iterative life cycle where more than one phase of the project might progress simultaneously. Requirements for a module can be gathered and analyzed before the module is designed and constructed. While analysis of a module is being done, the requirements gathering for another module could also start in parallel.
Similarly, a phase can be closed without the decision to initiate any other phases. For example, the project is completed or the risk is deemed too great for the project to be allowed to continue.
Formal phase completion does not include authorizing the subsequent phase. For effective control, each phase is formally initiated to produce a phase-dependent output of the Initiating Process Group, specifying what is allowed and expected for that phase. A phase-end review can be held with the explicit goals of obtaining authorization to close the current phase and to initiate the subsequent one. Sometimes both authorizations can be gained at one review. Phase-end reviews are also called phase exits, phase gates, or kill points.