A decomposition of an R-module into submodules, M = circle plus M-alpha, is
called deep if for every submodule H of M, we have H = circle plus(H boole
an AND M-alpha). We characterize when deep decompositions exist. We then sh
ow that M similar or equal to circle plus M-P (over all maximal ideals P) i
f and only if R/(Ann m) is a finite direct sum of quasi-local rings for all
0 not equal m is an element of M. We also show this decomposition is deep.