gistfile1.rb

class Extension
  include DataMapper::Resource
  
  property :id, Serial
  property :type_id, String, :length => 200
  property :requirement, String
  
  validates_is_unique :type_id, 
    :message => 
     "Extension with that type id already exists"
  validates_format :requirement, 
    :with  => /optional|mandatory/, 
    :message => 
     "Extension requirement must be optional or mandatory"
  validates_present :type_id, :requirement, 
    :message => 
     "An extension must specify a typeId and requirement"

  has n, :sections
end