From the start of a project, it is essential that an overriding system be implemented and adhered to that essentially governs all of the individual practices that take place within the life cycle of a given project. It is helpful to have an overriding principle that will allow project team members to know which way to lean when it comes to if the decision is ever in doubt. As a result of this, it is important to understand that the overall system here is typically referred to as the project methodology. The project’s overall methodology refers to an overriding and all encompassing system of techniques, concepts, procedures, practices, and rules that are to be adhered to whenever it is possible throughout the life cycle of a given project. The methodology of a project usually does not change from the point at which the project begins, although it is possible of course that the project methodology may shift from time to time as different phases of the project are completed.
This term is defined in the 3rd and the 4th edition of the PMBOK.