Only slightly related, there is no clearly defined concept of IDs ("identity"). It's not a technical issue. Identification is a tricky issue, influenced by hum

Only slightly related, there is no clearly defined concept of IDs ("identity"). It's not a technical issue. Identification is a tricky issue, influenced by human, social, and political decisions. It's also very easy to trick identification routines. A very practical example is email addresses for groups or organizations. It's not clear what's identified by such an administrative email address. The people who read it and send in its name? Some more abstract concept? Depends on the situation. I'm too tired to find a better example, but you get the idea... So the best thing is to say, email addresses identify, well, themselves, and also where to route emails to these adresses. You can't build technology without clear concepts. Or with too many, incompatible, concepts for that matter. I don't see a better way than layering (i.e separation of concerns).