The complete lattice of tripotents in a JBW*-triple and the unit ball in its predual are respectively proposed as models for the complete lattice of propositions and for the generalized normal state space of a nonassociative, noncommutative physical system. A subsystem of such a system may be defined in terms of either principal ideals in the complete lattice of propositions or norm-closed faces of the generalized state space. It is shown that the two definitions are equivalent and that each subsystem is associative.