- Short answer
There is no general rule - as the minimal amount depends on the system, its stakeholders, criticality, complexity, size and/or risks.
- Longer answer
We suggest to always explain, document or specify the following aspects:
- 3-5 central quality requirements, expressed in scenarios.
- Context view and external interfaces
- Brief explanation of your solution strategy, the most important decisions influencing the implementation or operation of the system.
- Building block view, level 1.
- Most important crosscutting concepts.