changeAttributes(ident uid, ident id, ident sheetId, double maxPoints) {
  assume exists //accounts/account[uid]/assistant[id];
 
  assume exists //exercises/exercise[id]/sheets/sheet[sheetId]; # implies the existence of the exercise
 
  assume maxPoints >= 0;
  assume //exercises/exercise[id]/students/student[x]/result[sheetId]/points <= maxPoints;
 
  update //exercises/exercise[id]/sheets/sheet[sheetId]/maxPoints maxPoints;
}