example associations between physical and proxy models

client_models.rb

class Ingredient < ActiveResource::Base

  def recipes
    # returns all recipes with this ingredient as a component
    Recipe.joins(components).merge(components)
  end

  def components
    Component.where :ingredient_id => id
  end
end

Class Component < ActiveRecord::Base

  belongs_to :recipe

  def ingredient
    Ingredient.find ingredient_id
  end
end

Class Recipe < ActiveRecord::Base

  has_many :components

  def ingredients
    # this might be better implemented by adding
    # a non-restful controller action on the server side
    component_ingredient_ids = components.map &:ingredient_id
    Ingredient.all.select { |i| component_ingredient_ids.include? i.id }
  end
end