A sheaf \({\mathcal{F}}\in {\mathsf{Sh}}(X; {}_{{\mathcal{O}}_X}{\mathsf{Mod}} )\) is quasicoherent if \(X\) is covered by open affine subsets \(U_{i}=\operatorname{Spec} A_{i}\) such that for each \(i\) there is an \(A_{i}\)-module \(M_{i}\) with \(\left.\mathcal{F}\right|_{U_{i}} \cong \widetilde{M}_{i}\), the sheaf associated to a module for \(M_i\).