All, I hope you're doing well. For the past couple months, me and several other people tried to identify how we could make PubSubHubbub better, by fixing some of its issues, but also opening the door to more use cases (private resources... etc). It is based on a lot of experience that we have accumulated by hosting some of the biggest hubs out there, but also conversations we've had with publishers who sometimes didn't go down the PubSubHubbub way.
We came to the conclusion that there was no way we could make 0.4 downward compatible because 0.3 makes too many assumption on the types of resources (Atom or RSS feeds). Here is a project of how the spec could evolve. We have already got a lot of feedback from people who implemented the previous spec but also from people who want to implement it now that it solves some of the issues. Git repo (feel free to check out): https://github.com/pubsubhubbub/PubSubHubbub/tree/future Human readable version at: https://superfeedr-misc.s3.amazonaws.com/pubsubhubbub-core-0.4.html I would personally appreciate your constructive feedback. Thanks, Julien
