The best way to understand sequence diagrams is to look at some examples of sequence diagrams. Sequence Diagram and Other UML Diagram Examples It's shown by an arrow going from a lifeline to an endpoint, a filled circle or an x. It can be shown by an arrow with an x at the end.Ī message sent from an unknown recipient, shown by an arrow from an endpoint to a lifeline.Ī message sent to an unknown recipient. This is a message that destroys an object. Similar to a return message, it's depicted with a dashed line and an open arrowhead that points to the rectangle representing the object created. 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. Export the diagram as PlantUML, Mermaid format file. Export the diagram as image (SVG, JPEG, PNG, TIFF). Navigate the code by click the diagram shape. Objects can be terminated early using an arrow labeled ">" that points to an X. SequenceDiagram for IntelliJ IDEA with this plugin, you can generate Simple Sequence Diagram. 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. I’ve just tried to reproduct the UML as is.Start Now Basic Sequence Diagram NotationsĬlass roles describe the way an object will behave in context. That might be something that we could consider modelling in the type system, but I haven’t bothered. Only certain locking types can be used with certain entitlement types. I have a feeling that there are some important business rules that have not been captured.įor example, if you read the comments in the source, you’ll see that there are some interesting constraints around EntitlementType and LockingType. This diagram is just pure data and no methods, so there are no function types. To demonstrate this in practice, I decided to scour the internet for some good (and not-so-good) UML class diagrams, and convert them into F# code. With UML diagrams, you need to translate them to code, with the possibility of losing something in translation.īut if the design is documented in your programming language itself, there is no translation phase, and so the design must always be in sync with the implementation. In a way that is easier to read, easier to write, and most important, easier to turn into working code! Instead, a concise language like F# (or OCaml or Haskell) can convey the same meaning Some UML diagrams are useful (I like sequence diagrams for example) and in general, I do think a good picture or diagram can be worth 1000 words.īut I believe that, in many cases, using UML for class diagrams is not necessary. Which is of course is a misquote of this famous scene. In my talk on functional DDD, I often use this slide ( in context):
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