This gem provides the railtie that allows datamapper to hook 
into rails3 and thus behave like a rails framework component. 
Just like activerecord does in rails, dm-rails uses the railtie 
API to hook into rails. The two are actually hooked into rails 
almost identically.

Creating new datamapper apps on rails3 from scratch is actually 
really easy. The following will guide you through the process.

WWW: https://github.com/datamapper/dm-rails