Asynchronously reporting 'un-processable' notifications

In the Madrid meeting we discussed how to notify a system that it has sent an "un-processable" notification. This was also discussed in the GitHub repository discussion forum.

The use case is that a system receives a notification which is "well-formed", and so the receiver sends a 202 Accepted response, queuing the notification for asynchronous processing. However, when the system attempts to process the notification, it discovers that it is "un-processable" for some reason. For example, a URL referenced in the notification might not be resolvable.

In this kind of use-case, HTTP error handling is not applicable, so the system needs a way to report the problem to the sender. The obvious approach is to send a notification explaining that a previously received notification is un-processable.

We have now published a new draft pattern for expressing this.

If you have comments or questions about this, please post them on this discussion forum thread.