I take the inspiration from Craig Larman book “APPLYING UML AND PATTERNS”.
- It is plausibile that you may want to add an extension which is not linked to a specific step.
Flow of Events
- Step1
- Step2
etc.
Extensions
*a At any time Manager requests an override operation:
- do something
- so something else
*b At any time system fails - do something
- so something else
- You may also want to add an extension for several steps
Flow of Events
- Step1
- Step2
- Step3
etc.
Extensions
1-3a: Customer asks Cashier to remove an item… - Cashier does something
- System display updated running total
- When you delete a step, the extension linked to it is deleted too. But you may want to associate that extension to another step or at least you would like to be asked for a confirmation, e.g. delete/keep/re-link to.