nLab semiseparated scheme

A cover $\{U_i\}_{i\in I}$ of a scheme by affine open subsets is semiseparated if $U_i\cap U_j$ is also affine for every pair $(i,j)\in I\times I$. An algebraic scheme is semiseparated if it has an affine cover which is semiseparated. The notion is introduced in

• Thomason, Trobaugh, in Grothendieck Festschrift 1989

category: algebraic geometry