What does "Top-Down" mean?

There seem to be several different ways people use the term top-down.

• Management hierarchy. Top-down means traditional command-and-control. See my post on Multiple Styles of EA.

• Decomposition/Refinement. Top-down means starting from broad vision and principles; bottom-up means starting with concrete detail and evidence. This is sometimes linked to the distinction between Analytic and Synthetic. In my post on SOA Chaos, I disagreed with Jeff Schneider's idea that analytic intelligence ("brains") was superior to synthetic intelligence ("grunts").

• Large versus small. Top-down means starting with the big pieces and assuming that the small pieces can be fitted into the gaps left by the big pieces. See Nick Malik's piece Should SOA be Top Down or Bottom Up, which I discussed in my post on Service Planning.

• Strategic versus tactical. See my post on Forest and Trees.

• Planned versus emergent. Top-down means directed and planned, bottom-up means collaborative and emergent. See my post on Emergent Architecture.

• TO-BE versus AS-IS. Top-down means starting from the future requirements of the business; bottom-up means starting from the available assets.

• Generic versus Specific. Top-down means starting from an apriori (generalized, enterprise-wide or industry-wide) schema (Kant); bottom-up means starting from the specific local requirements (Hume). This is a possible interpretation of Ali Arsanjani's posts on Kant versus Hume. See my post on The General and the Particular.

In very simple cases (such as the examples given in the books and training courses), these overlapping but logically distinct meanings of top-down may happen to coincide; but as things get more complex, the tension between competing notions of “top-down” will become more significant.

---

In a debate on community regeneration, Matthew Mckeague writes What I don’t think can be forgotten in the ‘bottom up’ ‘top down’ debate is that it shouldn’t be a binary choice. There’s a balance to be struck and professional skills and networks can’t be underestimated. It’s where the balance sits that we need some further debate.

See also The Politics of "Top-Down"


Updated 25 October 2019