Platform agnosticism

Ideally, templates should be platform agnostic. This means that if I define a template for 2 app servers, 1 db server, all talk to each other, I should be able to easily switch from AWS to local Vagrant without rewriting the template. Platform agnosticism is difficult to obtain, while at the same time, might not really be needed that often. Completely changing the underlying platform is a rather rare event that happens perhaps once or twice in a product's lifetime.