"Top down" vs. "bottom up"

Subject: "Top down" vs. "bottom up"
From: Randy Allen Harris <raha -at- WATARTS -dot- UWATERLOO -dot- CA>
Date: Tue, 5 Apr 1994 12:42:23 -0400

Ken d'Albenas asked

>Can someone enlighten me (and probably a few others too):
>what is "top down" design and what is "bottom up" design?
>I've often run across the terms in tech writing and
>other design contexts, but when I ask for definitions, the
>replies don't seem consistent.

Like all terms these ones have probably migrated in various directions in
various contexts, so what you're perceiving as lack of consistency may be
different definitions for different groups, and you'll probably get some
differing replies to your request, but ...

I know the terms from psychologinuistics, where they refer to parsing
strategies, and where sentences are assumed to have a hierarchical
structure or the following sort:

! !
! ____!___
! ! !
! ! NP
! ! ____!____
! ! ! !
! ! ! !
Bart is an underachiever

So, a top-down parse starts with the highest unit, the Sentence, and a
bottom-up parse starts with the lowest, the words. My guess is that all
top-down/bottom-up metaphors invoke a hierarchy, so that a top-down
management style would be one that starts with the CEO, bottom-up would
start with the workers, and so on.

-------======= * =======-------
Randy Allen Harris
raha -at- watarts -dot- uwaterloo -dot- ca

Rhetoric and Professional Writing, Department of English, University of
Waterloo, Waterloo ON N2L 3G1, CANADA; 519 885-1211, x5362; FAX: 519 884-8995

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