Message connectors: Use the Found Message shape in the UML shape library to start a sequence. Drag it box up or down the lifeline to move it. The activation shape will stay in place on the lifeline if you move it on the drawing canvas.ĭrag the start or end of the activation shape to shorten or lengthen it. There are several types of lifelines in the UML shape library.ĭrop a Destruction shape from the UML shape library on the end a lifeline to discontinue it, or use the Destruction Occurrence Specification shape in the UML 2.5 shape library.Īctivation boxes: Drop an Activation shape over a lifeline when the outline is purple to attach it. Lifelines: Drag the end of a lifeline to lengthen or shorten it. Click More Shapes at the bottom of the left panel, enable the UML and UML 2.5 libraries in the Software section, and click Apply. The UML 2.5 and UML shape libraries contain all the shapes you will need. There are several sequence diagram templates you can modify to start your sequence diagram faster. See the section on frame labels below for how to label and use the various types of sequence fragments. They are also used for parallel sequences or to indicate there is a critical single thread. Learn more about working with multi-page diagrams in draw.ioįrames can be used to show alternate sequences - ones that only execute if a certain condition is true. Add a link to that diagram page on the originating frame shape. Tip: Place each of these sequence fragment diagrams on their own diagram page in the same diagram file. If this is a complex sub-process, break it out into a separate diagram. Repetition or recursion - where part of a sequence or messages are repeated - is surrounded by a frame shape, also known as a sequence fragment. If a call message creates a new object instance, a new lifeline is added at that point. If an object instance is deleted before the overall sequence ends, its lifeline is terminated in an X. The box ‘starts’ when it first receives a message, and ‘ends’ when all messages have been sent/received and the process has been completed. When a system has to perform a process that takes some time to complete, use a vertical box on the lifeline (an activation box). The messages that pass between the lifelines are connectors - solid for an initial message or outgoing call, and dotted for a return value (optional). Open this sequence diagram in our diagram viewerĮach system/object instance and actor is placed on a lifeline - a vertical dotted line - going across the top of the sequence diagram. The further you progress down a sequence diagram, the more time has elapsed and the more events have occurred. Read a sequence diagram from the top down. However, they are still programming language neutral, and thus above the level of actual code. They are are closer to the actual code as they show all cross-system messages. Sequence diagrams extend use-case diagrams - they model the series of events that a scenario or use-case must execute. They are used to plan the development or extension of a software product and complement UML class diagrams, showing which class data is passed between which elements.

The events that cross system boundaries are used by objects and people (actors) to complete their processes.Īlso known as system sequence diagrams, they are one of the main types of UML diagrams. Sequence diagrams show the order of messages that are passed between elements of a system to complete a particular task or use case.

Sequence diagram uml loop