public function toList()
	{
		$list = array();
		$nodes = $this->getNodes();
		foreach( $nodes as $source )
		{
			$sublist = array();
			foreach( $nodes as $target )
			{
				if( $this->isEdge( $source, $target ) )
					$sublist[$target->getNodeName()] = $this->getEdgeValue( $source, $target );
			}
			$list [$source->getNodeName()] = $sublist;
		}
		return $list;
	}