  We investigate the single-spin asymmetries in inclusive and exclusive
processes of electron-proton scattering and electron-positron annihilation. In
the decomposition of hadronic tensor, a Lorentz symmetric spin-dependent term
is generally present. The existence of such a term implies single-spin
asymmetries in these processes and these single-spin asymmetries for baryons
can be understood in a unified manner. We argue that it is important to measure
the single-spin asymmetries in both inclusive and exclusive processes for the
$\Lambda$ production at the present B-factories. This will lead to the first
measurement of the structure function of the symmetric spin-dependent hadronic
tensor in these processes.
