Being a full-stack framework means that all layers are built to work seamlessly together. That way you Don’t Repeat Yourself (DRY) and you can use a single language from top to bottom. Everything from templates to control flow to business logic is written in Ruby—the language of love for industry heavy-weights.

In striving for DRY compliance, Rails shuns configuration files and annotations in favor of reflection and run-time extensions.

This means the end of XML files telling a story that has already been told in code. It means no compilation phase: Make a change, see it work. Meta-data is an implementation detail left for the framework to handle.