deleteTask(ident uid, ident id, ident taskId) {
  assume exists //accounts/account[uid]/examiner[id];
 
  assume exists //exams/exam[id]/tasks/task[taskId]; # implies the exam exists, which is implicitly true anyway
 
  assume size(//exams/exam[id]/results/participant/result[taskId]) = 0;
 
  remove //exams/exam[id]/tasks/task[taskId];
}