The User Requirement Specification (URS) specifies the requirements of the user for individual aspects of the facility, equipment, and systems in terms of function, throughput, operability, and applicable standards, what functions will be carried out, the data on which the system will operate, and the operating environment.
In practise there are both Functional requirements and Non-functional requirements
Non-functional requirements include constraints (eg project time scale) and what deliverables will be provided by the system ( documentation, training, testing, tools etc).
The URS is the stage at which the user's requirements are defined in sufficiently precise detail to allow suppliers to produce tenders for the work. This may involve a feasibility study.
The following guidelines should be followed during the production of the specification:
1. Each requirement statement to be uniquely referenced, and no longer than 250 words.
2. Requirement statements should not be duplicated nor contradicted.
3. The URS should express requirements and not design solutions.
4. Each requirement should be testable.
5. The URS must be understood by both user and supplier; ambiguity and jargon should be avoided.
6. Wherever possible, the URS should distinguish between mandatory/regulatory requirements and desirable features.
7. There may need to be a formal review of the URS between the user and supplier to check understanding and that requirements have been met (or not) in the Functional Specification.
A major part of the effort of producing good requirements specifications is defining the Functional Requirements