When a system is first conceptualized, architects should stay far away from listing any details of a system. The specifics of the type and structure of the data storage and UI should not be defined in the initial use cases. Has everyone forgotten about user testing? It shouldn't be an architect, but users who decides where each button should be placed and what data should be stored. By the time the developers get their hands on the use cases, they should have developed far beyond a simple diagram and should be a part of a detailed requirements document.