# Requirements for internet scale event notifications.
# What set of technologies can be leveraged to create an internet-scale notification service?
# What are the scaling factors for internet event notifications?
# What applications most benefit from an internet notification service?
# Security considerations for notifications.
"I'll see your GIF and raise you a Bloom Filter. Not that it in anyway detracts from the point of the article, which is to put more thought into resource design before jumping off into a new protocol."
Sparse bit arrays: "The solution, which I mentioned briefly at the talk, is to provide a resource that reflects all of the changes on Flickr during a given time period. Anyone (not just FriendFeed) can perform a GET on that resource to find out what has changed. In fact, one such example is the SUP (Simple Update Protocol) just introduced by FriendFeed. However, I had something more efficient in mind."