New polarized fragmentation functions are introduced and justified, in
addition to those conventional ones assumed to be independent of the helicity
of the parent parton. It is demonstrated that due to our present ignorance
concerning these new parton-spin dependent leading-twist fragmentation
functions, it is impossible to utilize current experiments on spin-dependent
semi-inclusive deep inelastic lepton nucleon scattering to disentangle the
separate polarized parton distributions.Comment: 8 pages, minor changes, 1 figure adde