There are a number of interesting differences between the Guide and PRINCE2 philosophies. PRINCE2 speaks of "stages" rather than "phases" and states that while the use of stages is mandatory, their number is flexible according to the management requirements of the project. 4 PRINCE2 also differentiates between technical stages and management stages. Technical stages are typified by a particular set of specialist skills, while management stages equate to commitment of resources and authority to spend. The two may or may not coincide. The Guide defines a project phase as: "A collection of logically related project activities, usually culminating in the completion of a major deliverable." It does.