A project life cycle is a collection of generally sequential project ______ whose name and number are determined by the control needs of the organization or organizations involved in the project. The life cycle provides the basic ______ for managing the project, regardless of the specific work involved. Simple系统集成公司据经验决定建立一套变更控制系统，为保证该系统行之有效，该系统中必须包括的内容是______。