Sequence diagrams are classified as interaction diagrams, and they visualize how objects collaborate, and focus on the order or time in which they happen. The end point is represented as a full circle, enclosed in a hollow circle, with an action flow arrow pointing towards it.Ĭheck out the comprehensive guide where we compare the Activity diagram with another UML diagram, State Machine. When both are used together, it is referred to as ‘synchronization’.įinal state (end point) – When the action sequence is finished, you reach the end point. Fork nodes split one action flow into multiple outgoing flows, and a join node combines multiple incoming flows into one outgoing flow. These conditions are called ‘guards’, and are largely optional.įork and join nodes – Fork and join nodes either split actions, or bring them together, and both are represented with thick, horizontal lines. Guard symbols – At decision nodes, there may be conditions that must be true before one of the actions can occur. Here, a decision must be made to determine the action flow. Objects are usually represented in rectangular boxes.īranches and decisions – When there are two or more possible outcomes to an action, this fork in the road is represented with a diamond shape. However, when the object flow arrow goes from an object to an action, it means that the action state uses the object in some way. When an object flow arrow goes from an action to an object, it means that the object was changed or created. Object flow – Sometimes, actions create or change objects. They are represented simply with an arrow, attached to a start point or action state.Īction/activity state – Usually in an oblong circle or unboxed, this is the action that is performed by an object. The arrow attached shows the first action that takes place when the sequence starts.Īction flow – These arrows show the flow of one action into another. Initial state (start point) – Represented by a small, filled-in circle, the start point is where the activity diagram begins. Notations and symbolsĪctivity diagrams have special UML symbols that easily tell the reader what the item is and which way the action flows. There are many UML symbols and notations used in activity diagrams, but these are some of the most common ones you’ll see. While they can be either concurrent or sequential, all activity diagrams have a beginning and an end state. They are similar to flowcharts, and show the outcomes of each action, and actions that happen after specific responses. Activity diagramsĪctivity diagrams show the order or flow of operations in a system. Make your own UML sequence diagram with Gleek. If you’re curious about other diagram types that use UML, read more about them in UML diagram types: everything you need to know and UML relationships articles. Why is this important? UML is used in both sequence and activity diagrams, along with many other types like class diagram, use case diagram, communication diagram, object diagram and etc. Universal Modeling Language, also known as UML, is a standardized language used in software diagrams to represent the items, processes, and relationships within a system. But, before we get into these two diagram types, we first need to talk about UML. Check out our UML Basics resource or any of the links below for more help learning how to make these diagrams and when to use them.Both activity diagrams and sequence diagrams are used by software developers to show actions and relationships within a software system. UML sequence diagrams are just one of many types of UML diagrams.
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How to add objects and lifelines to your sequence diagram.How to find shapes for UML diagramming in Gliffy.How do you make a sequence diagram in Gliffy? This quick tutorial teaches will teach you the basics of how to make a UML sequence diagram. UML Sequence Diagram Tutorial: How to Create a Sequence Diagram