  The essential points and physical backgrounds of the covariant
level-classification scheme, based on U(12)SF * O(3,1)L, are reviewed: This
scheme is extended from the non-relativistic SU(6)SF * O(3)L scheme by
introducing the new SU(2)-spin (rho-spin) degree of freedom, which is necessary
for covariant description of composite hadrons. Our scheme predicts the
existence of new type of chiral mesons and baryons (Chiralons) out of the
conventional SU(6)SF * O(3)L scheme. The sigma nonet is a typical example of
chiralons to be assigned to the q qbar relativistic S-wave state. The new
narrow mesons Ds(2317)/Ds(2463) are naturally assigned as the ground-state
scalar and axial-vector chiralons in the c sbar system.
