  If the narrow exotic baryon resonances $\Theta^+(1540)$ and
$\Xi_{{3/2}(1862)$ are members of the $J^P = {1/2}1/2^+$ antidecuplet with
$N^*(1710)$, the octet-antidecuplet mixing is required not only by the mass
spectrum but also by the decay pattern of $N^*(1710)$. This casts doubt on
validity of the $\Theta^+$ mass prediciton by the chiral soliton model. While
all pieces of the existing experimental information point to a small
octet-antidecuplet mixing, the magnitude of mixing required by the mass
spectrum is not consistent with the value needed to account for the hadronic
decay rates. The discrepancy is not resolved even after the large experimental
uncertainty is taken into consideration. We fail to find an alternative SU(3)
assignment even with different spin-parity assignment.
