Top Down vs. Bottom Up

There are several project delivery approaches that can be employed to build services.
The bottom-up strategy, for example, is tactically focused in that it makes the fulfillment
of immediate business requirements a priority and the prime objective of the project.
On the other side of the spectrum is the top-down strategy, which advocates the completion
of an inventory analysis prior to the physical design, development, and delivery
of services.

Figure 1 – A comparison of bottom-up and top-down delivery strategies.

As shown in the figure, each approach has its own benefits and consequences. While the
bottom-up strategy avoids the extra cost, effort, and time required to deliver services via
a top-down approach, it ends up imposing increased governance burden as bottom-up
delivered services tend to have shorter lifespans and require more frequent maintenance,
refactoring, and versioning.

The top-down strategy demands more of an initial investment because it introduces an
up-front analysis stage focused on the creation of the service inventory blueprint.
Service candidates are individually defined as part of this blueprint so as to ensure that
subsequent service designs will be highly normalized, standardized, and aligned.