Requirements baseline is the approved version of the requirements document that serves as a reference point for further changes. Requirements can be changed after they are baselined through a defined process that involves submitting a change request, analyzing the impact of the change, obtaining approval from the stakeholders, updating the requirements document, and communicating the change to the project team and other affected parties. Requirements can be changed at any stage of the project life cycle as long as they follow the defined process.Reference: = PMI Professional in Business Analysis (PMI-PBA) Examination Content Outline (2019), page 10; Business Analysis for Practitioners: A Practice Guide (2015), page 40.