TOPIC: Is the project schedule considered a part of the Project Management Plan or a part of the Project Documents?

Would you please clarify if the project schedule considered a part of the Project Management Plan or a part of the Project Documents? The reason I ask that on page 414 of Rita Mulcahy's book, she states the project schedule is part of the Project Documents. However I thought the project schedule is part of the Schedule Baseline, and the Performance Baselines are part of the Project Management Plan. The project schedule is an important component so I want to understand how the PMBOK categorizes it.