Including heavy quark production in ZEUS-PDF fits

At HERA heavy quarks may contribute up to 30% of the structure function $F_2$. The potential of including heavy-quark data in the ZEUS PDF fits is explored, using $D^*$ double differential cross-sections as well as the inclusive quantities $F_2^{c\bar{c}}$, $F_2^{c\bar{c}}$. The introduction of heavy quarks requires an extension of the DGLAP formalism. The effect of using different heavy flavour number schemes, and different approaches to the running of $\alpha_s$, are compared.