  This article reminds us the major contribution of orthogonality towards the
ESS assignment in TR-spectroscopy. In the field of particles, complete
orthogonality is ubiquitous between any two different identical particles, and
the complete orthogonality (at the microscopic level) evolves into the partial
spectral orthogonality between different ESSs at the mesoscopic level. As a
result, we developed SVD to TDSVD so as to reveal the relative amounts of
different ESSs in each time interval, and it is the first time that the single
solution can be drew from only the TA data set without any kinds of a priori
information. In the previous articles, the mathematical underdetermination
problem has been addressed prominently, so it is no wonder that researchers are
no longer keening to search the method for mathematically analyzing the data
set in order to derive the single solution. However, TDSVD will offset this
deficiency and becomes an effectively autonomous method towards two-dimensional
data analysis. Mathematically, as long as there is enough orthogonality between
any two 'ESSs' in any data set, the yield of the single solution is no longer a
problem. Therefore, TDSVD can be applied to lots of fields.
