db.rb

require 'rubygems'
require 'active_record'
require 'active_support'

ActiveRecord::Base.establish_connection(
                                        :adapter => :mysql,
                                        :socket => '/var/run/mysqld/mysqld.sock',
                                        :username => 'root',
                                        :database => 'ngrams',
                                        :password=> 'xxx'
                                       )

ngrams.rb

require 'db'

class BiGram < ActiveRecord::Base
end

class TriGram < ActiveRecord::Base
end

class QuadGram < ActiveRecord::Base
end