https://www.are.na/omar-rizwan/when-we-understand-that-slide-we-ll-have-won-the-war
(this feels like sort of a cheap shot, though, like when people complain that it's hard to make a formal grammar for Markdown or a formal semantics for C)
(when those are pretty simple to express as imperative code, and that's how their designs actually developed. similar here: these are really gnarly as Graphviz graphs but you could say it's just a poor representation)