deleteExam(ident uid, ident id) {
  assume exists //accounts/account[uid]/admin;
 
  assume exists //exams/exam[id];
 
  assume size(//acounts/account/examiner[id]) = 0;
 
  assume size(//exams/exam[id]/results/participant) = 0; # don't allow to delete if participants are there
 
  remove //exams/exam[id];
}