rails - what is the best/most efficient way to associate these models

In my application I have the following situation:

User belongs_to Group Group has_many Users

Project belongs_to User User has_many projects

The following is also true: - Each Group will have one BaseCase - Each Project will have multiple Scenarios and one BaseCase(depending on the开发者_高级运维 Group the Project User belongs to) - Scenario and BaseCase is the same type of object (let's call this Data) - The default values for each Scenario are the BaseCase values for the Group, but the User can change these default values to create the specific Scenario

I am not sure how to capture all these relationships through associations efficiently, does anyone have any ideas? thanks

If I understand correctly, then something like that

class User 
  belongs_to :group
  has_many   :projects
end 

class Group
  has_many :users
  has_many :projects, :through => :users
  has_one  :base_case
end

class Project
  has_many :scenarios
  has_one  :base_case
  belongs_to :user
  has_one :group, :through => user
  has_one :base_case, :through => :group
end  

class Scenario
  belongs_to :project
  has_one :base_case, :through => :project

  before_create do
    self.attributes = self.base_case.attributes.except(:group_id, ...)
  end
end

class BaseCase
  belongs_to :group
end