  Understanding how sea quarks behave inside a nucleon is one of the most
important physics goals of the proposed Electron-Ion Collider in China (EicC),
which is designed to have 3.5 GeV polarized electron beam (80% polarization)
colliding with 20 GeV polarized proton beam (70% polarization) at instantaneous
luminosity of $2 \times 10^{33} {\rm cm}^{-2} {\rm s}^{-1}$. A specific topic
at EicC is to understand the polarization of individual quarks inside a
longitudinally polarized nucleon. The potential of various future EicC data,
including the inclusive and semi-inclusive deep inelastic scattering data from
both doubly polarized electron-proton and electron-$^3{\rm He}$ collisions, to
reduce the uncertainties of parton helicity distributions is explored at the
next-to-leading order in QCD, using the Error PDF Updating Method Package ({\sc
ePump}) which is based on the Hessian profiling method. We show that the
semi-inclusive data are well able to provide good separation between flavour
distributions, and to constrain their uncertainties in the $x>0.005$ region,
especially when electron-$^3{\rm He}$ collisions, acting as effective
electron-neutron collisions, are taken into account. To enable this study, we
have generated a Hessian representation of the DSSV14 set of PDF replicas,
named DSSV14H PDFs.
