  The concept of spin-directed momentum provides a useful and restrictive
framework for describing dynamical mechanisms that can lead to single-spin
observables. The value of this framework can be demonstrated by consideration
of the polarizing fracture functions that characterize the production of
polarized baryons in the target fragmentation region of semi-inclusive deep
inelastic scattering from an unpolarized target. When Bjorken x is chosen large
enough to indicate a hard scattering from a valence quark, the fracture
function formalism dynamically selects a quark-diquark basis for baryon
structure. Attention to sonstituent orbital angular momentum in the formation
process and its role in contribution to the transverse momentum of the produced
baryon illustrates important aspects of the generation of polarization
observables.
