Hi, >The extension could indicate whether it's must-understand (such as >'copy') or may-ignore (such as 'metadata').
The 'may-ignore' extensions would have to be known when creating the specification. What about versions? The version to use is negotiated as follows: * client and server send the maximum version they support * they take the smaller of the two values in further communication In the case the server doesn't understand "copy node" (server version is 1), the client (client version 2) could send explicit add node commands, which are also understand in version 1, but are less efficient. Actually there could be multiple version number, for example a server and a client version, or a read and a write version (if the client version is too low, he might only be allowed to read but not write). Regards, Thomas
