Using a natural key, or using surrogate keys and audit table(s) for auditing/change log?

I agree with Rik. Yes, redundant data is very, very bad, evil, smelly, and otherwise undesirable. But just because two fields are called "phone number" does not make them the same thing.

"Customer's current phone number" and "Customer's phone number at the time we last spoke to him" are not necessarily the same thing at all.

I think you're being misled by a subtlety concerning the normal forms here. The thing is, the phone number associated with the callee is not the same piece of information as the number dialed by the caller. They might have the same value in the general case, but this is another issue.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.