2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/145656A class $\mathcal F$ of objects of an abelian category $\mathcal A$ is said to define a \emph{homological dimension} if for any object in $\mathcal A$ the length of any $\mathcal F$-resolution is uniquely determined. In the present paper we investigate classes satisfying this property.to appear in Contribution to Module Theory, de Gruyter 2007Rings and AlgebrasCategory Theory18G20; 16E10text