6. domain -- an optional parameter that specifies the machine that will receive notifications. If it is not specified, notifications are sent to the IP address the request came from.
Notes:
1. This change reflects reality in 2009. Aggregators may have multiple machines that receive notification, or the handler might move to a different IP address before the subscription expires.
2. It's only possible to make this change for the REST interface because there are XML-RPC and SOAP implementations that do not allow optional parameters.
3. You should send the domain parameter if your setup requires it, omit it if it doesn't.
4. It's essential that aggregators continue to poll periodically.
5. It's even more important that cloud servers test the notification handler before registering it.
6. My cloud server, rpc.rsscloud.org, has this change implemented on a provisional basis.
IMPORTANT: As of 9/13/09 this is a proposed change. You may implement it to evaluate it, but don't depend on it being the final method for implementing this functionality. It's possible we will find deal-stoppers before nailing this down.
