According to the PMI Guide to Business Analysis, the requirements baseline is a version of the requirements that has been formally reviewed and agreed upon by the stakeholders, and that serves as a basis for further development and validation activities. The requirements baseline is ready for sign-off when the requirements are clear, consistent, complete, and validated. These are the four characteristics of good requirements that ensure that they are understandable, unambiguous, accurate, and feasible. Complete means that the requirements cover all the necessary aspects of the business problem or opportunity, and that they do not have any gaps or omissions. Clear means that the requirements are expressed in simple and precise language, and that they avoid any jargon or ambiguity. Consistent means that the requirements do not have any conflicts or contradictions with each other or with the business objectives. Validated means that the requirements have been checked and confirmed by the stakeholders, and that they meet their needs and expectations. References: PMI Guide to Business Analysis, page 183-184.