  The superspace flatness conditions which are equivalent to the field
equations of supersymmetric Yang-Mills theory in ten dimensions have not been
useful so far to derive non trivial classical solutions. Recently, modified
flatness conditions were proposed, which are explicitly integrable
(hep-th/9811108), and are based on the breaking of symmetry SO(9,1) ->
SO(2,1)xSO(7). In this article, we investigate their physical content. To this
end, group-algebraic methods are developed which allow to derive the set of
physical fields and their equations of motion from the superfield expansion of
the supercurl, systematically.
  A set of integrable superspace constraints is identified which drastically
reduces the field content of the unconstrained superfield but leaves the
spectrum including the original Yang-Mills vector field completely off-shell. A
weaker set of constraints gives rise to additional fields obeying first order
differential equations. Geometrically, the SO(7) covariant superspace
constraints descend from a truncation of Witten's original linear system to
particular one-parameter families of light-like rays.
