Diagrams are next to useless in my experience. They tell you nothing about the execution of the system, it's properties, invariants, etc. If diagrams were all

Diagrams are next to useless in my experience. They tell you nothing about the execution of the system, it's properties, invariants, etc. If diagrams were all we needed to design software we'd all be writing UML right now and proving our systems correct with it. A better alternative is to look into specification languages and the awesome tooling around them. Unit-B, TLA+, etc.