Useful high level talk used for façade and command pattern

Useful high level talk used for façade and command pattern:

There are two approaches to deal with services and other cross-cut concerns, one is top-down approach, and another is bottom-up approach. We need both approaches.

By using top-down and bottom up, we do not need to get into details, and we implies (correctly) there are only two, and we need both of them for different situations (we all know that we have larger projects and smaller projects).