| A use case diagram shows the grouping of services provided by the system to the users. | |
| An arrow from an actor to a use case shows which actor starts the use case. | |
| The best grouping of functions into use cases depends on a number of factors. Beware of over decomposition. | |
| The basic flow is the most important course of events or what happens most of the time. | |
| Simple numbered sentences should define mostly interactions across the system boundary in the use case text. | |
| The source and target of the interaction should always be included in the sentence that defines it. | |
| Simple iteration may be defined in a use case flow using a single sentence. |