The complete lattice of tripotents in a JBW-triple and the unit ball
in its predual are respectively proposed as models for the complete la
ttice 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 compl
ete lattice of propositions or norm-closed faces of the generalized st
ate space. It is shown that the two definitions are equivalent and tha
t each subsystem is associative.