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UML 2.5.1

UML diagrams: all 14 types explained

Fourteen diagram types in UML 2.5.1, one article each, every one of them with real diagrams rather than descriptions of diagrams.

15 articles112 min read

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What is UML?

The Unified Modeling Language in practice: the fourteen diagram types, how structure and behaviour split, and how to pick the right diagram for the question you are actually asking.

9 min read

Read in order

Every UML diagram, explained

  1. 02Class diagramsHow to read and draw a UML class diagram: the three compartments, visibility markers, multiplicity, and the difference between association, aggregation, composition, generalization and realization.Structure diagrams11 min read
  2. 03Sequence diagramsHow to read and draw a UML sequence diagram: lifelines, activation bars, synchronous and asynchronous messages, replies, and the combined fragments (alt, opt, loop, par) that handle branching.Behaviour diagrams10 min read
  3. 04Use case diagramsHow to read and draw a UML use case diagram: actors, the system boundary, associations, and the include and extend relationships that people most often get backwards.Behaviour diagrams8 min read
  4. 05Activity diagramsHow to read and draw a UML activity diagram: actions, decisions and merges, forks and joins, guards, swimlanes, and the difference between a branch and true parallelism.Behaviour diagrams9 min read
  5. 06State machine diagramsHow to read and draw a UML state machine diagram: states, transitions with trigger, guard and effect, entry and exit actions, composite states, and history pseudostates.Behaviour diagrams9 min read
  6. 07Component diagramsHow to read and draw a UML component diagram: components, provided and required interfaces, ball-and-socket notation, ports, and how it differs from a class diagram.Structure diagrams8 min read
  7. 08Deployment diagramsHow to read and draw a UML deployment diagram: nodes, devices and execution environments, artifacts, communication paths, and the deploy relationship.Structure diagrams7 min read
  8. 09Object diagramsHow to read and draw a UML object diagram: instance specifications, underlined names, slots with concrete values, links, and how to use one to sanity-check a class diagram.Structure diagrams6 min read
  9. 10Package diagramsHow to read and draw a UML package diagram: packages, import and access dependencies, merge, nesting, and using the dependency direction to enforce a layered architecture.Structure diagrams6 min read
  10. 11Composite structure diagramsHow to read and draw a UML composite structure diagram: parts, ports, connectors, delegation, and the difference between this and a class or component diagram.Structure diagrams6 min read
  11. 12Communication diagramsHow to read and draw a UML communication diagram: objects, links, numbered messages, nested decimal sequencing, and when to prefer it over a sequence diagram.Behaviour diagrams6 min read
  12. 13Timing diagramsHow to read and draw a UML timing diagram: lifelines as value axes, state-change waveforms, duration and time constraints, and when elapsed time matters enough to need one.Behaviour diagrams6 min read
  13. 14Interaction overview diagramsHow to read and draw a UML interaction overview diagram: interaction occurrences, inline interactions, control flow between them, and how it keeps large sequence diagrams manageable.Behaviour diagrams5 min read
  14. 15Profile diagramsHow to read and draw a UML profile diagram: stereotypes, metaclasses, the extension relationship, tagged values, and when extending the language is better than working around it.Structure diagrams6 min read

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