public function addChild(Form_ElementModel $Child)
	{
		$cp = (array) $Child->parents; // child parents
		$fp = (array) $this->parents; // fieldset parents
		foreach($fp as $parent => $condition)
			$cp[$parent] = $condition;
		$Child->parents = $cp;
		$index = count($this->children);
		$this->children[] = $Child;
		if(isset($Child->id))
			$this->id2index[$Child->id] = $index;
		if(isset($Child->name))
			$this->name2index[$Child->name] = $index;
	}