In construction, a part that governs the form
of the rest; for example, Japanese room sizes
are traditionally governed by multiples of
standard tatami floor mats; today
prefabricated buildings are mass-produced in
a similar way. The components of a spacecraft
are designed in coordination; for example,
for the Apollo Moon landings the craft
comprised a command module (for working,
eating, sleeping), service module
(electricity generators, oxygen supplies,
manoeuvring rocket), and lunar module (to
land and return the astronauts).