createTask(ident uid, ident id, ident taskId, double maxPoints) {
  assume exists /account[uid]/examiner[id];
 
  assume exists /exam[id]; # implicitly true in OO implementations
  assume not exists /exam[id]/task[taskId];
 
  assume maxPoints >= 0;
 
  insert /exam[id] <task id=[taskId] maxPoints=[maxPoints] />;
}