PlantUML – UML Diagramming Tool

This looks like a great set of tools to create different types of UML diagrams from simple text representations. Uses Graphviz for some diagram types.

https://plantuml.com/

Quoting their website

PlantUML is a component that allows to quickly write :

• Sequence diagram
• Usecase diagram
• Class diagram
• Object diagram
• Activity diagram (here is the legacy syntax)
• Component diagram
• Deployment diagram
• State diagram
• Timing diagram

The following non-UML diagrams are also supported:

• JSON data
• YAML data
• Network diagram (nwdiag)
• Wireframe graphical interface (salt)
• Archimate diagram
• Specification and Description Language (SDL)
• Ditaa diagram
• Gantt diagram
• MindMap diagram
• Work Breakdown Structure diagram (WBS)
• Mathematic with AsciiMath or JLaTeXMath notation
• Entity Relationship diagram (IE/ER)