  Physics perspectives are shown for future experiments in electron or positron
scattering on nucleons, towards a deep and comprehensive understanding of the
angular momentum structure of the nucleon in the context of Quantum
Chromodynamics. Measurements of Generalised Parton Distributions in exclusive
reactions and precise determinations of forward Parton Distributions in
semi-inclusive deep inelastic scattering are identified as major physics
topics. Requirements are discussed for a next generation of high-luminosity
fixed-target experiments in the energy range 30-200 GeV.
