'asynchronous' events in use case

[vjr]

Just wondering how people model the situation where the user can perform an action during a step being performed by the system.

For example:
1. User asks system to initiate (ongoing) process A
2. System starts performing process A (which keeps going until explicitly stopped)
3. User asks system to stop process A

During step 2 the user can adjust some parameter of process A, that the system must take into account.

I had something like (simplified):

Alternate Flow : Adjust Inputs
Prior to step 3 of the Main Flow, the user can adjust input values:
1. user changes value XYZ
2. return to main flow

But it's not really an 'alternate' flow for step 3, or any other step.

I guess there are 2 questions here: how to word an ongoing process in a use case; and how to model the situation described above.

[philchudley]

I would use an activity diagram with an interruptable region surrounding the steps where the user coluld adjust the parameter.

Capture the request to adjust as an "Accept Event", connection to the setting action with an "Interupt Flow", then resume the flow just before the interrupt region.

Alternatively, the behaviour could be modelled using a State Machine Diagram capturing the events as triggers on transitions

Cheers

Phil

[vjr]

Thanks. I guess the point is that not everything can be put into use case text/prose. I was trying to massage EA into generating the correct activity diagram for me from the structured scenario. One thing you can't do is to have one activity join back to a decision point (rather than an activity) which you can do manually.

[sargasso]

You have three use cases.
Start Process A
Tell Process A
Stop Process A

Please continue.
b