  The KdV equation models the propagation of long waves in dispersive media,
while the NLS equation models the dynamics of narrow-bandwidth wave packets
consisting of short dispersive waves. A system that couples the two equations
to model the interaction of long and short waves seems attractive and such a
system has been studied over the last decades. We evaluate the validity of this
system, discussing two main problems. First, only the system coupling the
linear Schr\"odinger equation with KdV has been derived in the literature.
Second, the time variables appearing in the equations are of a different order.
It appears that in the manuscripts that study the coupled NLS-KdV system, an
assumption has been made that the coupled system can be derived, justifying its
mathematical study. In fact, this is true even for the papers where the
asymptotic derivation with the problems described above is presented. In
addition to discussing these inconsistencies, we present some alternative
systems describing the interaction of long and short waves.
