In the A-SPICE, there are various kinds of requirements; System Requirement, System Design, SW Requirement, SW architecture, SW Unit design. ISO 26262 requires similarly .
To manage traceability rigid decomposition of requirements into these are beneficial.
You can integrate all kinds of requirements into one documents. Then you will face a fact that managing traceability is not a easy task.
To specify, it requires different kinds of technical skills. It is not related engineering knowledge. It is closely related to logical thinking and writing technique.
You may wonder if I emphasize that writing technique is core skill to comply engineering process, because writing technique seems not to be related to engineering knowledge.
To Know it and to explain what you know are different. Sometimes it takes much time or infinite time to understand a document, because it is hard to understand. Requirement obfuscation is not good for team’s productivity and team’s communication. It also makes hard to achieve A-SPICE or functional safety standard.
So, engineers are required to learn how to specify requirements. It shall be educated.
To engineers, please do not blame readers because of their poor engineering knowledge, and do not think that it is a reason they do not understand your document. It is not good.
- Requirements_Engineering_Management_Handbook explains how to specify requirements.
- safety driven model based system engineering methodology(Part 1, Part 2) shows example.
- AUTOSAR Use Case Example CP Release 4.3.1