A change log is a document that records and tracks the changes that are made to the project scope, schedule, budget, or quality. It helps the project manager to monitor and control the project performance and ensure that the changes are aligned with the project objectives and stakeholders' expectations. A change log can also include information such as the change description, impact, status, approval, and date. A change log is the best source for the PM to use to confirm the assertion that the functionality request was rejected during the planning phase, as it would show the details and reasons for the rejection12.