Simple answer: it depends. Different companies doing development (pure tech to Fortune level corporations) all have different requirements and environments. A

Simple answer: it depends. Different companies doing development (pure tech to Fortune level corporations) all have different requirements and environments. A small, fast-pivoting, ever changing start-up isn't going to need, want or have the time for all the detailed documentation a large, regulated Fortune X company will require. That said, I think a knowledge of UML is beneficial to all levels, if just having a common modeling "language". Start-ups can use selected diagrams (eg, sequence, deployment, component) to develop, work out and "document" the high-level vision, and maybe major bugs. Keep them light on details and flexible. Like a paper road-map, they show only the major things, and don't require much time to update. Large and maybe regulated corporations (and even start-ups in regulated industries) will not only need, but require deeper levels of detail. Class, state and other diagrams. They get into the city-street level maps. But again, they can afford the levels of bureaucracy staffing (like "enterprise architects") required to maintain all the documentation.