* http://gmp.example.com/a/group#role => RSS with members of that role
* use SAML metadata to manage keys for TLS or setup OAuth
* A feed is a dynamic set of users - a provided group
* A channel is a set of feeds created by a user in an SP in order to manage ACLs and content
* Feeds are autocreated as people login to the SP bringing with them epe values. 
* A feed come in several flavours: json, atom, etc depending on the gmp
* Feeds are updated in the background
* Feeds contain a set of cached users
* A channel is a users view of a set of feeds, feeds are what gmp's provide to SPs

content negotiation

- http://gmp.example.com/a/group.atom#role => RSS/ATOM (+activity stream)
- http://gmp.example.com/a/group.json#role => JSON metadata for the feed

- http://gmp.example.com/a/group#role
- http://gmp.example.com/a/group