Does the activity diagram describe a single system activity or does it specify the various system activities?
Can there be more than one start in the activity diagram? Ex: Starts an activity with a regular user but also initiates an activity with a special user.
The activity diagram describes the sequence of activities involving software, showing from user actions to completion of software functions.
Intheexampleabove,Idescribeasimpleactivitydiagramofarentalcompanythatusesleaseregistrationsoftware,whichIfollowfromtheactionofanactorrequestingthelease,proceedingwiththestepsthatsuperficiallydescribethefunctionsofthesoftwarewithdecisionpointsusuallyreferredtotheactor.
Soinshort,theactivitydiagramdescribesallthefunctionalityofthesoftwaredescribingtheactivitiesthatleaduptoitsexecutionanduntilthecompletionofitsexecution.(Intheaboveexample"Request allocation" does not refer to the software itself, but to the employees of the store, usually along with the activity diagram is attached a table describing each functionality better.
The activity diagram can have more than one beginning and more than one end. It describes the execution flow of a specific activity of the system, and can cover another activity as long as this second activity is necessary for the execution of the first activity.
The activity diagram represents the flow from one activity to another, it is a flow diagram.
According to my knowledge it is not possible to have more than one start, what can be there is two streams waiting for the other to start, but they can not start in parallel.
