cook has_many :mappings
cook has_many :datapoints, :through mappings
cook has_many :cookers, :through mappings
cook has_many :sensors, :through mappings

mappings belongs_to :cook
mappings has_one :sensor
mappings has_one :cooker
mappings has_many :datapoints, :through :sensor

datapoint belongs_to :sensor
datapoint has_one :cook

sensor has_one :type
sensor has_many :mappings
sensor has_many :cooks, :through :mappings

cooker has_many :mappings