Writing a functional requirements document (frd) is an essential step in the software development process. [provide a list of contractual or task level assumptions and/or constraints that are preconditions to preparation of the frd. To help you upsurge towards your business goals, we suggest you to try using a business requirements document. [provide a list of contractual or task level assumptions and/or constraints that are preconditions to preparation of the frd. Assumptions are future situations beyond the control of the project,.