And we must, above all, figure out how to communicate the skill; which may not be a matter for declarative statements alone. Martial artists spar with each other, execute standard forms, and are watched throughout by their teachers. Calculus students do homework, and check their answers. Olympic runners continually try to beat their best previous time, as measured by a stopwatch.

Hmm, I haven't seen much progress here on that side. There are a few small calibration tests on the web that have been linked now and then, but not many real exercises.