  Poincare' covariant definitions for the spin-dependent spectral function and
for the momentum distributions within the light-front Hamiltonian dynamics are
proposed for a three-fermion bound system, starting from the light-front wave
function of the system. The adopted approach is based on the Bakamjian-Thomas
construction of the Poincare' generators, that allows one to easily import the
familiar and wide knowledge on the nuclear interaction into a light-front
framework. The proposed formalism can find useful applications in refined
nuclear calculations, like the ones needed for evaluating the EMC effect or the
semi-inclusive deep inelastic cross sections with polarized nuclear targets,
since remarkably the light-front unpolarized momentum distribution by
definition fulfills both normalization and momentum sum rules. It is also shown
a straightforward generalization of the definition of the light-front spectral
function to an A-nucleon system.
