where here P − − and M contain interactions. The transverse components of the light-front spin, j → → ⊥ ⊥ may or may not have an interaction dependence; however, if one also demands cluster properties, then the transverse components of total spin necessarily have an interaction dependence. The result is that by choosing the light front components of the spin to be kinematic it is possible to realize full rotational invariance at the expense of cluster properties. Alternatively it is easy to realize cluster properties at the expense of full rotational symmetry. For models of a finite number of degrees of freedom there are constructions that realize both full rotational covariance and cluster properties; these realizations all have additional many-body interactions in the generators that are functions of fewer-body interactions.