  Suppose $X$ and $Y$ are Banach spaces, and ${\mathcal{I}}$, ${\mathcal{J}}$
are operator ideals (for instance, the ideals of strictly singular, weakly
compact, or compact operators). Under what conditions does the inclusion
${\mathcal{I}}(X,Y) \subset {\mathcal{J}}(X,Y)$, or the equality
${\mathcal{I}}(X,Y) = {\mathcal{J}}(X,Y)$, hold? We examine this question when
${\mathcal{I}}, {\mathcal{J}}$ are the ideals of Dunford-Pettis, strictly
(co)singular, finitely strictly singular, inessential, or (weakly) compact
operators, while $X$ and $Y$ are non-commutative function spaces. Since such
spaces are ordered, we also address the same questions for positive parts of
such ideals.
