Deep-inelastic production of heavy quarks at HERA, especially charm, is an
excellent signal to measure the gluon distribution in the proton at small x
values. By measuring various differential distributions of the heavy quarks
this reaction permits additional more incisive QCD analyses due to the many
scales present. Furthermore, the relatively small mass of the charm quark,
compared to the typical momentum transfer Q, allows one to study whether and
when to treat this quark as a parton. This reaction therefore sheds light on
some of the most fundamental aspects of perturbative QCD. We discuss the above
issues and review the feasibility of their experimental investigation in the
light of a large integrated luminosity.Comment: 10 pages, uses epsfig.sty, five ps figures included. To appear in the
proceedings of the workshop Future Physics at HERA, eds. G. Ingelman, A. De
Roeck and R. Klanner, DESY, Hamburg, 199