Modeling bookkeeping app in Rails

keeps_books_models.rb

class Account < ActiveRecord::Base
  acts_as_tree
  belongs_to :asset_type
  has_many :transactions  
end

class AssetType < ActiveRecord::Base
  has_many :accounts
end

class Transaction < ActiveRecord::Base
  belongs_to :account
  has_many :transactionships
  has_many :matches,
    :through => :transactionships,
    :after_add => :add_inverse,
    :after_remove => :remove_inverse
end

class Transactionship < ActiveRecord::Base
  belongs_to :transaction
  belongs_to :match, :class_name => "Transaction", :foreign_key => "match_id"
end

class Person < ActiveRecord::Base
  belongs_to :person_type
end

class PersonType < ActiveRecord::Base
  has_many :people
end