question: private void unifyViaAtom ( Atomic parentAtom ) { Atomic childAtom = getRuleConclusionAtom ( ) ; Query parent = parentAtom . getParentQuery ( ) ; Map < String , String > unifiers = childAtom . getUnifiers ( parentAtom ) ; head . unify ( unifiers ) ; body . unify ( unifiers ) ; Set < String > childFVs = body . getVarSet ( ) ; Set < String > parentBVs = parentAtom . getVarNames ( ) ; Set < String > parentVars = parent . getVarSet ( ) ; parentBVs . forEach ( null ) ; childFVs . forEach ( null ) ; }
target:  propagate variables to child via a relation atom (atom variables are bound)