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Subscribing to updates to a URL is an extremely useful building-block for the indieweb.
Later, after updating http://example.org/
Problems with this flow
Ideal solution: a content-agnostic, pure-HTTP hub-based approach.
Publishers create content on the web, and let hub(s) know that it exists/when it’s updated via a POST request. Content is published with a Last-modified header.
Hubs periodically poll the content for changes (HEAD request and Last-modified header inspection) just in case they missed any updates/to enable pubsub of content published by people who for whatever reason can’t notify the hub.
Publishers publicly declare which hub manages notifications for their content via a Link header or HTML/XML element with rel=hub.
When a subscriber wants to subscribe to changes to a URL, they discover the hub as described above, and send a POST request to some endpoint (/subscribe?) with the URL they’re subscribing to and the URL they want notifications sent to.
Then, when a publisher updates their content and either a) sends a notification to the hub or b) the hub polls the URL and sees the Last-modified header change, the hub sends POST requests out to all the subscribers for that URL.
Benefits over current solutions