  We propose a theory for doped antiferromagnet based on a bosonic
resonating-valence-bond (RVB) state with incorporating the phase string effect.
Both antiferromagnetic (AF) and superconducting phase transitions occur
naturally within such a bosonic RVB phase. Two distinct metallic regions --
underdoping and optimum-doping -- are also found to be a logic consequence,
whose unique features explain the recent neutron-scattering measurements in
cuprates.
