With the help of Davy Mitchell, and the input of others on the backstage discussion list (Tony Hirst, Duncan Barclay, and others) we have put together the first proof of concept of Feed Annotation Streams (formerly known as RSS Annotation Streams). The idea is simple - consumers of a feed create annotations for that feed, the put those annotations in a new feed that refers to the original items by guid.
The example is based on the BBC RSS news feed and Davy's mood score (is the news good or bad?) for the articles. The RSS feed is consumed in DataSphere and geotagged, the items are then referenced against the mood score FAS and coloured. The colouring I applied is very simple. If the sum of the mood scores for a location is positive, the pin is painted green, negative red and zero white.
There is a lot still to do in terms of defining the spec, but it looks like it has great potential.
The Feed Annotation Stream looks something like:
<annotationStream feedURL="original-feed-url" annotationURI="URI-for-annotation-service" feedRead="date" annotationStreamWrite="date">
<!--annotation information here-->