Our ‘plain text’ is unfortunately not up to the task of representing all human written text; I'm thinking specifically of traditional mathematical notation, whi

Our ‘plain text’ is unfortunately not up to the task of representing all human written text; I'm thinking specifically of traditional mathematical notation, which is also a tree structure represented in two dimensions, and ancestral to programming notation, in that we first squeezed mathematical notation down to one dimension¹ and then augmented it with notations for control flow. ¹with a few forgotten exceptions like the Klerer-May system.