Summary: ENES489P Activity and Sequence Diagrams 09/30/2010
Modeling Behavior using Activity and Sequence Diagrams
In this lab, you will be creating behavior models of two different systems. Activity and sequence diagrams are good
at capturing aspects of behavior that is discrete and synchronous. Activity diagrams are better at depicting branching
behavior while sequence diagrams are good for depicting communication between objects. Both will be used in this
One interesting problem that arises is that if there are two representations of behavior, one given in activity diagrams
and one in sequence diagrams, the models can contradict each other. Carefully consider this as you develop your
models of behavior.
Develop an set of diagrams for an ATM machine depicting a number of scenarios. A scenario will be captured by a
sequence diagram. Since there are multiple possible behaviors, multiple scenarios will be required.
Your model may include this hypothetical scenario for withdrawing money from an account:
The customer goes to the ATM machine insert the card to the machine and enter the pin number. The Bank (Control
system) authorizes the user and if that is a valid customer let the customer to enter the value for the withdraw otherwise,
the transaction ends and the machine returns the card.
For the next step the control system check the available balance and process the transaction if possible (assuming the
system does not let the balance to become negative). If the transaction is impossible, an error message is displayed
and the system prompts to enter another transaction. At any time when prompted to enter a transaction, the user may
cancel, at which point the ATM machine will close the session and eject the card.