Extensible Messaging and Presence Protocol (XMPP) is an open messaging standard, perhaps best known in its use for cross-platform instant-messaging application interoperability.
The core part of XMPP is now an IETF RFC: RFC-6120.
XMPP has a PubSub protocol for social-networking, as defined in XEP 0060.
All content throughout the XMPP network has a unique URI. Here's a list of common URI representation of resources:
- user: xmpp:user@host
- PubSub node: xmpp:pubsub.host?;node=nodeName
- PubSub publication: xmpp:pubsub.host?;node=nodeName;item=ae890ac52d0df67ed7cfdf51b644e901
- massive spec
- no one has ever fully implemented it
- there's no comprehensive (or even feature covering) test suite
- everyone who tries to implement it, only ever implements a subset of it
- interop requires testing with every implementation you want to interoperate with (instead of just with a standard test suite)