This is a message that creates a new object. Like synchronous messages, they are drawn with an arrow connecting two lifelines however, the arrowhead is usually open and there's no return message depicted.Ī reply message is drawn with a dotted line and an open arrowhead pointing back to the original lifeline.Ī message an object sends to itself, usually shown as a U shaped arrow pointing back to itself. It's usually drawn using a line with a solid arrowhead pointing from one object to another.Īsynchronous messages don't need a reply for interaction to continue. Ī synchronous message requires a response before the interaction can continue. Place the condition for exiting the loop at the bottom left corner in square brackets. When that object's lifeline ends, you can place an X at the end of its lifeline to denote a destruction occurrence.Ī repetition or loop within a sequence diagram is depicted as a rectangle. Objects can be terminated early using an arrow labeled ">" that points to an X. Lifelines are vertical dashed lines that indicate the object's presence over time. Asynchronous messages are sent from an object that will not wait for a response from the receiver before continuing its tasks. Use half-arrowed lines to represent asynchronous messages.
Messages are arrows that represent communication between objects. When an object is busy executing a process or waiting for a reply message, use a thin gray rectangle placed vertically on its lifeline. Use the UML object symbol to illustrate class roles, but don't list object attributes.Īctivation boxes represent the time an object needs to complete a task. Start Now Basic Sequence Diagram NotationsĬlass roles describe the way an object will behave in context.
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