removeResult(ident uid, ident id, ident studentId, ident taskId) {
  assume exists //accounts/account[uid]/examiner[id];
 
  assume exists //exams/exam[id]/results/participant[studentId]/result[taskId];
    # implies the exam, account, student role and task exist by integrity
 
  remove //exams/exam[id]/results/participant[studentId]/result[taskId];
}