Foundations of a theory of convexity on affine Grassmann manifolds
Jacob Eli Goodman, Richard M. Pollack · Mathematika · 1995
this paper is to define this structure and to develop its most important properties. This is not mere "generalization for its own sake": there are many questions involving configurations that have been answered in the case of points, or in the case of hyperplanes, but that become difficult or perhaps intractable when the points are replaced by intermediate-dimensional flats, such as lines in R