My illustration of why AR migrations suck and DM properties don't

migrationssuck.rb

# Migrations are ugly and make you write a lot of code you don't need.
#in AR
  # from http://wiki.rubyonrails.org/rails/pages/UnderstandingMigrations
  class AddANewTable < ActiveRecord::Migration #these 3 lines
    def self.up #are just a very verbose way to say
      create_table :users do |table| # to make a table
        table.column :name, :string
        # This column will contain an MD5 hash.
        table.column :login,  :string, :null => false
        table.column :password, :string, :limit => 32, :null => false
        table.column :email, :string       
      end
    end
def self.down
drop_table :users
end
end

# in DM
#in your model
include DataMapper::Resource #just 1 line
#let's treat what essentially act like instance variables like instance variables!
property :id, Serial #in DM, you could even have a String id! AR strongly discourages it. and there are composite keys
property :name, String
property :login, String, :nullable => false
property :password, String, :length => 32, :nullable => false #you call the maximum length 'length'!
property :email, String

# basically, it's prettier, less code, and more semantic, and the model's properties are in the model file.