Download UML Sequence Diagrams - Lecture Notes | CSIS 360 and more Study notes Civil Engineering in PDF only on Docsity! CSIS 370 – Lecture 4 UML Sequence Diagrams Class diagram shows the classes in a system, and how they are related, but it is static. The UML includes some dynamic diagrams also, which show what goes on in a system while it is executing. Instead of classes, the sequence diagram shows objects. It shows how objects interact as the system is executing. Elements of sequence diagram: - Objects drawn along the top of the diagram. Naming syntax object:Class. - Time flows from the top to the bottom - Each object has a lifeline while it exists. Objects can be created and destroyed during the time shown in the sequence diagram. - The lifeline is drawn as a dashed line while the object is inactive, and as a narrow rectangle while it is active. - Communication between objects represented using horizontal arrows between the object's lifelines. Last week we looked at this use case, and came up with a class diagram that had the following classes: Product, ShoppingCart, LineItem. Let's look at how we would develop the sequence diagram for this use case and class diagram. Title: Add product to shopping cart Level: User Goal StakeHolders: Customer Preconditions: Customer has searched for and found desired product Main Success Scenario: 1. Customer selects AddToCart Button 2. System uses product number to add a line item (quantity 1) to the customer's shopping cart (which may be empty or already contain items). 3. System displays the contents of the shopping cart, with unit prices, line prices, and total price (not including shipping or taxes) Extensions: 3a. If the item is out of stock, the system displays a message indicating this below the item in the shopping cart, along with an estimated shipping date. Instance form: describes the flow of one particular scenario from a use case Generic form: describes all flows in a particular use case description. Let's look at an example of the instance form first. Let's try to draw the sequence diagram for the Main Success Scenario
