Address the handling of atom id elements when POSTing to collections. Allow clients to indicate their desire that the server generate the id.
Servers are free to do what they want with atom:id when clients POST to collections but what they choose to do has a powerful effect on functionality. For most implementations, allowing the client to set id or request that the server generate an id is the optimal behavior. APP clients will need a way to indicate their desire to have atom id generated by the server.
Add the following lines to Section 3
sentinel id - The IRI reserved for use in the atom id element to indicate a client's desire that the server generate a new value for the atom id element. The IRI is: http://www.purl.org/atom#autogenerated-id
Add the following as Section 8.2.1
8.2.1 Handling Atom Id When POSTing an entry to a collection, the client MAY use the setinal id (see Section 3) to request that the id be generated by the server. The server SHOULD either replace the id or return a 4XX status code. Servers SHOULD leave POSTed atom id elements unchanged in other cases to allow entries to be moved from one collection to another. Please refer to [AtomFormat] for a detailed description of the semantics of the atom id element.