Policies from experience

Hi everyone, I am curious regarding the use of "policies", rules or goals to manage a network at the three levels: business, traffic engineering and routing. I have these questions: 1) What examples of policies could be enforced at each level? (the simplest case being that of routing policies using EGP that I can think of)? 2) Could there be a clear cut in terms of policies between these three levels: business, routing and TE ? 3) anyone using the Routing Policy Specification Language (RPSL) ? Thank you for taking the time. Djamel Sadok