Note this is touched upon in the serialization documentation under "To Do" or "Ideas for new projects" I forget which. Robert Ramey Terdale, Shantibhushan wrote:

I am trying to use XML serialization for streaming data on network. I could understand that with versioning you can make any class backward compatible. I have a situation which demands the other way; I need to read and construct an old object from new XML data. Currently it throws stream_error exception for any newly added member. I am trying to figure out how to deal with it; either write new archive or derive from existing XML archive and do changes etc.

I am wondering whether anybody has done any work towards this idea and would like to share their insight.

Thanks Shanti