public function transform()
	{
		if( !( $this->xml && $this->xsl ) )
			throw new InvalidArgumentException( 'XML and XSL must be set.' );
		$xml	= DOMDocument::loadXML( $this->xml );
		$xsl	= DOMDocument::loadXML( $this->xsl );
		$proc	= new XSLTProcessor();
		$proc->importStyleSheet( $xsl );
		$result =  $proc->transformToXML( $xml );
		return $result;
	}