bottom-up implementation n. Hackish opposite of the techspeak term `top-down design'.

bottom-up implementation n.

Hackish opposite of the
techspeak term `top-down design'. It has been received wisdom
in most programming cultures that it is best to design from higher
levels of abstraction down to lower, specifying sequences of action
in increasing detail until you get to actual code. Hackers often
find (especially in exploratory designs that cannot be closely
specified in advance) that it works best to build things in
the opposite order, by writing and testing a clean set of primitive
operations and then knitting them together. Naively applied, this
leads to hacked-together bottom-up implementations; a more
sophisticated response is `middle-out implementation', in which
scratch code within primitives at the mid-level of the system is
gradually replaced with a more polished version of the lowest level
at the same time the structure above the midlevel is being built.