There is (and always has been) quite a bit of interest in calendaring at the moment - why? Well, apart from the obvious "all existence is there" it's something that can be as simple or as complex a problem as you want it to be; and it has very practical applications.
Other people have collected requirements elsewhere - these are mine. (Brainstorm format.)
Given the raw requirements, I've attempted to refine them into a set of criteria that form a basis for a critique of any existing specification, protocol or product.
The rest of this is work in progress or to do - feel free to contribute suggestions or pointers directly or, better still, to the mailing list.
What is out there: other people and organisations doing work in this area.
What is out there: standards and other documents in this area (with critiques).
What is out there: products (free or otherwise) with critiques and capabilities.
Do we need to do something more? Something new? Detailed requirements to go here.