Lifecycle vs. Process

What is the relationship between a project's lifecycle (PP SP 1.3) and the project's process, which is part of the project plan (PP SP 2.7 and GP 2.2 for all PAs). I realize that the lifecycle is used to determine decision points or project milestones. However, doesn't the project's process used also determine that? If a project selected a waterfall lifecycle, wouldn't a very high-level description of the project's process also be do requirements, design, code and test.

The project's software development lifecycle (SDLC) specifies managable project phases, such as analysis, design, code, and test. The SDLC is one of the necessary components, along with the tasks, activities, and work products, that are used to estimate the scope, effort, and cost for the project. Each project phase usually concludes with a decision point and/or project milestone. The project's processes govern the tasks and activities that occur within and across each lifecycle phase. The project processes do not determine when project milestones occur and neither do they determine which project milestones occur. These two aspects of the project are determined by the SDLC.

The other aspect of the project's SDLC is that the project's processes are a function of the SDLC chosen for the project. If the project uses a waterfall SDLC, the project's processes would be very different from those needed to support an agile SDLC.