  We report on results of Kra\'skiewicz and the author, and Watanabe on KP
modules materializing Schubert polynomials, and filtrations having KP modules
as their subquotients. We discuss applications of KP filtrations and ample KP
bundles to positivity, due respectively to Watanabe and Fulton. The article
corresponds to the talk given by the author at the conference "IMPANGA 15" in
April 2015.
