public function validate($xmlString, $schemaFile=null)
	{
		$doc = $this->_loadXmlDoc($xmlString);
		$originalUseErrors = $this->_setupValidationErrorHandling();

		$isValid = $doc->schemaValidate($schemaFile);
		$errors = $this->_retrieveErrors();
		$this->_teardownValidationErrorHandling($originalUseErrors);
		if (!$isValid) {
			throw Mage::exception('Radial_RiskService_Sdk_Exception_Invalid_Payload', $this->_formatErrors($errors));
		}
		return $this;
	}