hierarchy.rb

class Programme < AR::Base
  has_many :villages
  has_many :conversations, though: :villages
end

class Village < AR::Base
  has_many :discussions
  has_many :conversations, through: :discussions
end

class Discussion < AR::Base
  belongs_to :village
  has_many :conversations
end

class Conversation < AR::Base
  belongs_to :discussion
  has_one :change
end