Currently:

TBall: 1 relation
SPS:   several relations forming an implication tree
FPS:   several relations

TBall subset
NEW:

SPS':   at least two relations forming a single implication tree
FPS':   at least two relations not forming a single implication tree

Evolution with NEW:

TBall
TBall + SPS' = SPS
SPS' : testing implication tree software
TBall + SPS' + FPS' = FPS
FPS' : testing multiple independent relations software