I am translating a Use Case diagram step into an Activity Diagram. Does every step of my UC diagram describe an Activity ? Is there one and only one Activity in an Activity Diagram ?

  • Provide some more details (concrete use case diagram and your activity diagram attempt). In general use case represents something complex with several steps and several actors involved while activity is more like one function call
    – xmojmr
    Commented Jun 14, 2015 at 7:46
  • Usecase diagram focus on model system and user interaction while activity diagram focus on work flow. There are more than one activity for your system.it is depend on system.
    – AjayGohil
    Commented Oct 26, 2020 at 4:24

1 Answer 1


An activity is an ongoing nonatomic execution within a state machine. The ovals on an activity diagram are either action states or activity states. Action states are the atomic execution of an operation. Activity states are nonatomic and can be decomposed on another activity diagram. So, no, there does not have to one and only only activity per activity diagram. And, no, every step of a use case does not necessarily correspond to an activity. They may be action states or activity states or possibly neither.

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