public function ElementsByName( $names )
	{
		if ( is_string( $names ) )
			$names = array_map( 'trim', explode( ",", $names ) );

		if ( ! is_array( $names ) )
			throw new Exception( 'InstanceElementsFilter::ElementsByName $names must be a string or array' );

		$names = array_flip( $names );
		return new InstanceElementsFilter( $this->instance, array_intersect_key( $this->elements, $names ) );
	}