private static function init()
{
if (self::$NULL_SCOPE === NULL) {
self::$NULL_SCOPE = new Scope();
self::$DEFAULT_SCOPES = array();
foreach (self::$DEFAULT_SCOPE_VALUES as $defaultUnitTag => $defaultValue) {
if (strlen($defaultValue) > 0) {
self::$DEFAULT_SCOPES[$defaultUnitTag] = self::parseValue($defaultValue);
} else {
self::$DEFAULT_SCOPES[$defaultUnitTag] = self::$NULL_SCOPE;
}
}
}
}