PlantUML is not directly supported by GitHub, but its still possible. Basically we pass your puml file to PlantUML to generate, and they return a PNG which gets included in the page

• Generate you .puml file in the usual way using your favorite editor and confirm the diagram is as you want it.
• Save the file to the assets directory
• Then paste the following into you Markup.

PlantUML is a text descriptive language which gets converted into UML and other types of graphs So this :-

@startuml

Bob->Alice : hello

@enduml

would produce this :-

A more complex example :-

![PlantUml flowchart](http://www.plantuml.com/plantuml/proxy?cache=no&src=https://raw.github.com/Kf-GaryNewport/Kf-GaryNewport.github.io/master/assets/test.puml)