Craft externalizes nothing and transfers by apprenticeship. Engineering writes the governing relation down where someone else can find it wrong.

Four times now I have written the same three sentences in different notations, for four problems

that looked unrelated: a design method, a coding technology, an architecture-derivation procedure,

and a contract-modelling tool. I noticed the repetition only after the fourth. Here it is, stated

as precisely as I can manage.