x1 is a basis/foundation/underlying or fundamental principle of x2; x1 is at the bottom of x2.
x2 is founded on basis x1 (= selcmu for reordered places); (adjective:) x1 is basic/basal/fundamental); (generally events and properties will be bases for events and states, while objects may be bases/bottoms for objects). See also cmavo list ji'u, jamfu, zbepi, genja, krasi.