Designer, implementor, user, writer A Fragment by Donald Knuth dl.acm.org Thus, I came to the conclusion that the designer of a new system must not only be the implementor and the first large-scale user; the designer should also write the first user manual. The separation of any of these four components would have hurt TeX significantly. If I had not participated fully in all these activities, literally hundreds of improvements would never have been made, because I would never have thought of them or perceived why they were important. Eating your own dog food making
Invisible substance We wanted wood, not only in many visible places, but also in the roof trusses of the homeroom buildings, where they are invisible. Fujita wanted to replace the invisible trusses with steel trusses. They could not understand the idea that it was the actual substance — even though not visible — which would control the feeling of the thing. Christopher Alexander, The Battle for the Life and Beauty of the Earth All the way throughFinished on the inside material