/** @param string $aString must be alpanumeric */
	function addFieldProp($name, $type, $readOnly=false, $minValue=null, $maxValue=null, $minLength=0, $maxLength=null, $classDir=null, $persistent=true)
	{
		if (strlen($name)==0) {
			trigger_error("addFieldProp without a name", E_USER_WARNING);
			return null;
		}

		$clsDes = $this->getClassDescriptor();
		$prop = new PntFieldPropertyDescriptor($name, $type, $readOnly, $minValue, $maxValue, $minLength, $maxLength, $classDir, $persistent);
		$clsDes->addPropertyDescriptor($prop);
		return $prop;

	}