  We describe a long term project aimed at deriving information on the chemical
evolution of the Galactic disk from a large sample of open clusters. The main
property of this project is that all clusters are analyzed in a homogeneous
way, to guarantee the robustness of the ranking in age, distance and
metallicity. Special emphasis is devoted to the evolution of the earliest
phases of the Galactic disk evolution, where clusters have superior reliability
with respect to other types of evolution indicators. The project is twofold: on
the one hand we derive age, distance and reddening (and indicative metallicity)
interpreting deep and accurate photometric data with stellar evolution models,
and, on the other hand, we derive the chemical abundances from high-resolution
spectroscopy. Here we describe our overall goals and approaches, and report on
the mid-term project status of the photometric part, with 16 clusters already
studied, covering an age interval from 0.1 to 6 Gyr and Galactocentric
distances from 6.6 to 21 kpc. The importance of quantifying the theoretical
uncertainties by deriving the cluster parameters with various sets of stellar
models is emphasized. Stellar evolution models assuming overshooting from
convective regions appear to better reproduce the photometric properties of the
cluster stars. The examined clusters show a clear metallicity dependence on the
Galactocentric distance and no dependence on age. The tight relation between
cluster age and magnitude difference between the main sequence turn off and the
red clump is confirmed.
