Document: NUREG-0800
Document ID: fea61ff0-f344-4101-adfb-590e3d9dfafe
Document Type: srp
Title: Draft Revision 6 – August 2015
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1515/ML15159A946.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
. Style means that the contents of the SRS are understandable. The SRS should differentiate between requirements placed on the software and other supplementary information, such as design constraints, hardware platforms, and coding standards. A precise definition of each technical term should exist, either in the SRS or in a separate dictionary or glossary. Each requirement should be uniquely and completely defined in a single location in the SRS. Traceability means that a two-way trace exists between each requirement in the SRS and the safety system requirements and design. There should be a two-way trace between each requirement in the SRS and the software design, as well as a forward trace from each requirement in the SRS to the specific inspections, analyses, or tests used to confirm that the requirement has been met. Unambiguity means that each requirement, and all requirements taken together, have one and only one interpretation. Verifiability means that it is possible to construct a specific analysis, review, or test to determine whether each requirement has been met. B.3.3.1.3 Review Guidance for SRSs Errors in requirements or misunderstanding of requirement intent are a major source of software errors. The requirements should be carefully examined by the reviewer, and each of the above functional characteristics should be present in each requirement. If the requirements are not clear to the reviewer, they will probably not be clear to the software design team. The thread audit discussed above is a tool which can be used to check each of these characteristics. During the thread audit, for each requirement traced, the reviewer should check that each requirement is complete, that the requirements are consistent with the overall safety system requirements, and that the requirement is not in conflict with some other requirement. The requirements should be understandable and unambiguous. Each requirement should be traceable to one or more safety system