Guides
26 guides on uml. Practical writing from the team building Atlas, useful whether or not you buy anything.
UML spans a dozen diagram types with strict rules, so "supports UML" hides enormous variation. This framework helps you judge UML tools by the notation and workflows you will actually use.
Any object that moves through defined states (an order, a subscription, a document) is a state machine hiding in your code. Drawing it makes the illegal transitions obvious before a bug allows one.
The hardest part of UML is not the notation but knowing which diagram to draw. Match the diagram to the question and the rest gets easy.
UML and the C4 model are not rivals so much as tools for different jobs. Knowing which one fits the audience in front of you is the whole decision.
UML defines fourteen diagram types, but you will use a handful of them constantly and the rest rarely. This guide covers all fourteen and tells you which ones actually earn their place.
An ER diagram and a UML class diagram can look almost identical (boxes with fields, lines between them) yet they answer different questions. Knowing which to reach for saves confusion.
A state diagram captures how an object moves between states over its lifetime. PlantUML writes one as states and transitions, with support for guards, composite states, and concurrency.
A component diagram shows the high-level building blocks of a system and how they plug together through interfaces. PlantUML makes one from components, interfaces, and connectors written as text.
A use case diagram answers a simple question: who can do what with this system. PlantUML makes one from a few lines of actors, use cases, and the relationships between them.
A class diagram captures the static structure of an object-oriented design. PlantUML lets you write one as text, with precise control over members, visibility, and every relationship type.
Sequence diagrams are where PlantUML shines, because it lays them out itself rather than deferring to Graphviz. This tutorial takes you from a two-line diagram to loops, alternatives, and activation bars.
PlantUML lets you write a diagram as a few lines of text and get a rendered UML diagram back. This guide covers the syntax, the diagram types, and how to make it part of a workflow that stays current.
An object diagram is a snapshot of specific instances at one moment in time. This guide explains how it complements the class diagram and when a concrete example is worth a thousand abstractions.
You do not need to be an engineer to read a UML diagram. This guide decodes the four types you are most likely to meet, in plain language, so you can follow along in any design discussion.
SysML is a modeling language built on UML but aimed at whole systems, not just software. This guide compares the two, explains what SysML adds, and helps you decide which you need.
The lines in a class diagram carry as much meaning as the boxes. This guide explains every relationship type, the notation for each, and simple tests for choosing the right one.
UML has fourteen diagram types split into two families: structural diagrams for what a system is, and behavioral diagrams for what it does. This guide maps them all and helps you pick.
Deployment diagrams show where software actually runs: the physical nodes, the artifacts deployed on them, and the connections between them. This guide covers nodes, artifacts, and modern cloud topologies.
Component diagrams show how a system decomposes into replaceable parts and the interfaces they expose and consume. This guide covers components, ball-and-socket interfaces, ports, and dependencies.
State machine diagrams model how an object moves between states in response to events. This guide covers states, transitions, guards, entry and exit actions, and nested composite states.
Activity diagrams model workflows and business processes with the rigor of UML. This guide covers actions, decisions, concurrency with forks and joins, and swimlanes for responsibility.
A use case diagram maps who uses a system and what they use it to do. This guide covers actors, use cases, boundaries, and the include and extend relationships that trip people up.
Sequence diagrams show how objects collaborate over time by exchanging messages. This guide covers lifelines, message types, activation, and the fragments that model real control flow.
The class diagram is the most useful diagram in UML. This guide covers everything on the box, every line between boxes, and how to draw one that clarifies rather than clutters.
UML is a shared visual language for describing software before you build it. This guide covers what it is really for, all 14 diagram types, and how to use the handful that earn their keep.
Class diagrams model the structure of object-oriented code. Mermaid lets you write them in text and keep them next to the code they describe.
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