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  1. ΥΠΕΥΘΥΝΟΣ:ΘΟΔΩΡΗΣ ΜΑΝΑΒΗΣ UML Intro, Activity Diagrams

  2. Activity diagrams The Activity Diagram is the UML version of the classic flowchart. It is a component of the use case diagrams and can be used to explain a use case or a series of use cases. • Activities and transitions • Guard conditions • Decisions • Merge points • Start, End • Concurrency • Activities and transitions: Activity is a step in a process where some work is getting done. Activities are linked with each other with transitions Provide credit card data Pay by credit card • Guard conditions: We use them when we want to show that some transitions must only happen if a condition is valid. An example • Decisions… are represented by diamonds. Each option in a decision is modeled with a guard condition. Each guard condition must be mutually exclusive (= αμοιβαία αποκλειόμενη)

  3. Activity diagrams • Decisions (continued): Decisions can also be represented without the diamonds, as possible transitions coming from an activity: • Merge point: The place where 2 alternative paths come together and continue as one. Uses the diamond notation just like the decisions. (not always necessary) • Start, End: There may exist more than one end points, but only one start point.

  4. An online bookshop (a case study) The system gives the user the ability either to log on, or, if he/she is a new customer register for the first ime and then log on. The customer provides his/her username and password and if they are correct the system logs him/her on. He can view items and place them in his/her shopping cart. When he/she finishes, he/she can proceed to the checkout or log off the system. The system prompts the user to finalize his shopping cart (i.e. asks the customer if he/she wants to add or remove any other books). Then, the system provides the user with information on possible delivery dates for the books he selected (some books may take a long time to deliver, so the customer needs to be warned of that). If the customer agrees to the proposed delivery dates, he/she proceeds to the payment stage (by credit card only). The system validates the credit card and creates the order, updates the inventory and provides the customer with an "electronic receipt" via email. For the above system we are going to draw the activity diagram. See the following slide:

  5. An online bookshop (Activity diagram)