A functional specification document (fsd), also known as a functional requirements document (frd), is considered by many project management and software. Assumptions are future situations beyond the control of the project,. A user requirements document, written by the product manager, is centered around the end user’s needs and expectations for a product.it translates user requirements into. The frd is produced by business analysts or sometimes the technical team in response to the business. [provide a list of contractual or task level assumptions and/or constraints that are preconditions to preparation of the frd.