gaphor: gaphor (Simple UML and SysML modeling tool)
gaphor:
gaphor: Gaphor is a UML, SysML, RAAML, and C4 modeling application. It is 
gaphor: designed to be easy to use, while still being powerful. Gaphor 
gaphor: implements a fully-compliant UML 2 data model, so it is much more 
gaphor: than a picture drawing tool. You can use Gaphor to quickly visualize 
gaphor: different aspects of a system as well as create complete, highly 
gaphor: complex models. Gaphor provides four modeling languages: UML, SysML, 
gaphor: RAAML and C4 and makes them accessible to beginners.
gaphor: https://github.com/gaphor/gaphor