Today I learned that the diagram style that shows two or more vertical lines with actions going from line to line is called a sequence diagram, and it’s a UML thing (we never got in to UML when I was in college).

Then I discovered PlantUML, which takes plain text input (like Graphviz dot files), and spits out pretty sequence diagrams, complete with annotations, time delay indicators, and more.

Neat.

Bob->Alice : Knock knock
Alice->Bob: Who's there?
Bob->Alice: A non-sequitur
Alice->Jim: What?
PlantUML, sequence diagrams