I want a mechanism to determine if two party's view of a collection are equivalent. I want to be able to query if an object is contained in a collection without enumerating the whole collection. I want a mechanism to request re-delivery or maybe failed delivery notifications.
For what it's worth, these are all goals that would align well with the interests of a broad set of implementors. I make a little noise now and again about the SWICG forum task force, but directly addressing some of these concerns would definitely be on our radar.
Current focus is on aligning on a common object type for higher level collections (the context), but I'm thinking that Collection (ordered, ideally) would be the best fit and also allow for future use cases like you mentioned earlier.
You have the ideas, we might be able to supply the coordination...
smallcircles