Many web resources provide mechanisms for subscribing to changes in their content. However, this change information is only made available via a polling mechanism.
A number of people have proposed mechanisms for subscribing to updates to pages or feeds, however, a missing element of all these proposals is a subscription mechanism. Sadly, this means that every site supporting this feature will likely end up with a different implementation.
Get Pingd pour la mise à mort de la syndication... (à coups de XRDS, d'Atom et de web hooks, tout un programme)
AtomOwl is an ontology whose aim is to capture the semantics of rfc4287. RFC4287 is a format to syndicate online content, such as weblogs, podcasts, videocasts, etc. Syndication is a helpful way to alert interested readers to changes to a web site, be it to new content or changed content.
what about SIOC ?