  We report our progress on the data analysis of $\pi\pi$ scattering data in
terms of Forward Dispersion Relations (FDR), as well as Roy equations (RE) and
their once-subtracted counterpart, GKPY equations. The first part of the
analysis consists of independent fits to the different $\pi\pi$ channels. The
GKPY equations provide a more stringent consistency check for the
parametrizations of the S0-wave data in the region from 400 to 1100 MeV, In the
second part we present our preliminary analysis where the fits are constrained
to satisfy all dispersion relations within errors, including the new GKPY Eqs.,
thus providing a very precise and model independent description of data using
just analyticity, causality and crossing.
