The goal of this research project is to obtain a global and precise view of protoplanetary disks. This DiskEvol program will tackle the complex problem of combining consistently the constraints on the gas phase of a disk, provided by the Herschel observations, with our existing studies of the dust phase. This is of particular importance as the dissipation of abundant gas remnant from star formation limits the timescale for giant planet formation, controls the dynamics of planetary bodies during their formation and determines the final architecture of the planetary system. This proposal will rely on 1) the preparation of a database of chemistry and radiative transfer models for the Herschel GASPS Key Program project. This initial work will allow 2) a detailed analysis of the GASPS program through a statistical comparison of the GASPS observations with the predictions from the grid of models. This global study, of the large sample of disks observed by GASPS, will be 3) extended and completed through finer detailed modelling of a selected sample of representative sources for which we will obtain a complete view of the dust structure and gas chemistry using simultaneous interpretation of continuum observations, resolved emission maps in low-level rotational lines of CO, in addition to follow-up observations with HIFI, a high-spectral resolution instrument onboard Herschel. DiskEvol will provide an unprecedented inventory of gas and dust in protoplanetary disks, transforming our understanding of disk evolution by addressing key questions on the timescales and main mechanisms of dust and gas evolution within disks. This project offers a unique opportunity to bring back to the LAOG the expertise in line radiative transfer gained during the initial Marie Curie Fellowship in Exeter. In addition, the long-lasting value of DiskEvol results is of exceptional importance in the era of ALMA and JWST.