bottom-up

adjective2

1. •
   Of or relating to a hierarchical system that progresses from multiple small subunits to a single, large basic unit.

   • The software is checked very carefully in a bottom-up fashion. First, each new line of code is checked, then sections of code or modules with special functions are verified. — 1986
2. •
   Of or relating to a hierarchical system in which lower levels influence higher levels.