![]() They are commonly things like objects (instances of classes), actors (objects of interest outside the system), systems, subsystems, components, or even use cases. The lifelines represent instances (or roles that instances play) of any classifier in the UML. The object lifelines represent objects playing roles in a collaboration and the stimuli show the messages sent between the lifelines over time. The most important elements are the object lifelines and the stimuli (or messages). ![]() Callouts identify the different elements of the sequence diagram. And finally, during testing, sequence diagrams can be used to specify expected behavior (given a set of preconditions and an ordered set of stimuli) and validate output.įigure 1 shows a sequence diagram depicting the interaction of instances of the elements from the class diagram in the article mentioned earlier. During system modeling, sequence diagrams are used to demonstrate how internal structural elements interact to provide higher level behavior, such as to “realize” a use case. During requirements capture, they can help define messages sent between the actors and the system, their allowable sequences (sometimes called the “protocol of interaction”), and quality of service constraints. Please someone correct me if there is any misunderstanding.Sequence diagrams can be used in a number of ways during the software development process. Finally, the cart object will invoke the placeItemInOrder function of the inventory object to place the checked out items in order. Next, the storefront will acknowledge this message, meaning that the order has been confirmed and then an acknowledgment will be sent by the cart order to acknowledge the checkout process. Next this "self function " will invoke the confirmOrder method of the storefront object. Next, this cart object will invoke its processorder function to process the order. After that ,the storefront object will send a message for the cart object to make the checkout of these items that are added to the cart from the for loop. Next, this inventory object will acknowledge the cart object and the cart object will acknowledge the storefront object for adding this item. ![]() For certain storefront ( object of storefront class, say amazon ), there will be a loop for each item or stock available at this storefront, every item will be added to a certain object of cart class and this cart object will call a certain inventory object to reserve this item (call reservethisitem method of that belongs to this object). I understand that this diagram describes the operation of buying some items from certain storefront. Else, if the value is less than 1000, the other distributor "regular" will dispatch this item. In other words, we will send a message or call the dispatch function of the careful object of the distributor class. After that for each item in this order (loop), for if the value of this item is more than 1000 we will make the careful distributor (certain object of distributor class) to dispatch this order. First of all, there will be a dispatch message for certain order (object of order class). Can you confirm if my understanding is correct ?Īccording to my understanding, this sequence diagram describes the dispatch process of orders to either of two distributors. I am trying to understand two sequence diagrams that I have found in the SE course at university of Washington. ![]()
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