Also as I have coverd some in RFC 47, many of the attributes will have well chosen defaults which allow for shorter argument lists for common situations. There is no special interface required, you just specify a callback attribute. That makes the request automatically non-blocking and registers the event for you. All of them are covered in under this approach and adding new attributes is easy and won't conflict with other code written to this specification. Implementation should be very straightforward.
Some work has to be done with managing which module supports which attributes.
No new syntax or semantics are added. Common Callback API for all AIO calls.