[DonRotolo]

Exactly. For another example of What before How:

Requirement: Ability to drive cars on the driveway after a snowfall.
Capability: Remove snow from my driveway.
Methods: Melt snow. Push snow. Throw snow. (etc...)
Mechanisms: Hot air guns. Electric wires that get warm. Big magnifying glass to focus solar energy. Hot water heater. Propane torch. Use chemicals to lower melting point. (etc. And that's just the "melt" method...)

Last, from all the mechanisms, you find the one that's "best" (which can be debated) and build it.