UML Sequence Diagram Tutorial

What is a UML sequence diagram? UML sequence diagrams are used to represent or model the flow of messages, events and actions between the objects or components of a system. Time is represented in the vertical direction showing the sequence of interactions of the header elements, which are displayed horizontally at the top of the diagram. Sequence Diagrams are used primarily to design, document and validate the architecture, interfaces and logic of the system by describing the sequence of actions that need to be performed to complete a task or scenario. UML sequence diagrams are useful design tools because they provide a dynamic view of the system behavior which can be difficult to extract from static diagrams or specifications. Although UML sequence diagrams are typically used to describe object-oriented software systems, they are also extremely useful as system engineering tools to design system architectures, in business process engineering as process flow diagrams, as message sequence charts and call flows for telecom/wireless system design, and for protocol stack design and analysis. See also common mistakes to avoid when using sequence diagrams. This tutorial describes the basic drawing elements used in sequence diagrams and when they are used. These are the diagram elements that are supported by the Sequence Diagram Editor tool. Some are not part of the UML specification and may not be supported by other UML tools. The header portion of the sequence diagram represents the components or objects of the system being modeled and are laid out horizontally at the top of the diagram. See an example sequence diagram here.