My biggest problem with generated ID's, though, is that it is hard to do merge's with them without working it out programatically (as marina pointed out) because there isn't a way to replace the old objects with the new ones because they won't share the same pk.
What do you think of a mechanism where I am completely in control of creating primary keys and making them unique? For example, I KNOW each server ID will be unique and I KNOW each cpu ID will be unique within it's server so that I can just assigned a pk id to the cpu of "serverID+cpuID" (ie "A1", "A2", etc)...
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