a more traditional mechanism for articulating a specific customer goal for system use and the interaction sequence(s) needed to achieve the goal; associated with software engineering
emphasis on user-system interactions, rather than user's task itself identify &"actors&"  define the &"normal course&"  id alternative courses with #s corresponding to steps replaced
are the mechanism for capturing the desired behavior for the system that is under development, but they do not specify how the behavior is to be implemented.