This plugin helps you to serialize your records into very short strings for storing in cookies.

class Product
  include DataMapper::Resource
  property :id,   Serial
  property :name, String
end

class OrderItem
  include DataMapper::Resource
  is :serialized
  has 1, :product
  property :id,    Serial
  property :name,  String
  property :count, Integer, :default => 1
  property :used,  Boolean, :default => false
  property :note,  Text
  serialize_properties :count, :note # GeneralSerializeFilter is default value
  serialize_property :product, ModelSerializeFilter
  serialize_property :used, BooleanSerializeFilter
end