Question

How would you model the references and citations to publications (articles, books, chapters, etc…)?

A publication can be an article, book or a chapter and it has many references to other publications and other publications refer to it (call these citations)

I need to be able to list the relationships among the publications: The references in a publication and the citations from other publications to this publication

My initial understanding is that this would be a polymorphic relationship to handle the different types of publications and that it would require a bidirectionalself join.

My stab at it

Publication belongs_to :writing, :polymorphic =>true has_and_belongs_to_many :references     :class_name => 'Publication'    :join_table => 'reference_citation'     :foreign_key => 'reference_id'    :foreign_key => 'citation_id'  Book,    Chapter,    Article all have: has_many :publications :as =>writing 

I find this a bit confusing so any suggestions that would help clarify it would be great. Even object and field naming suggestions.

[I asked a less clear version of this question here.]

I also probably need to use has many through because I will need the ability to destroy the relationship

Answer 1

Here’s a solution using a self-referential relationship using single table inheritance. Use these commands to create the app:

$ rails myproject $ cd myproject $ script/generate model publication type:string name:string $ script/generate model citation publication_id:integer reference_id:integer 

The setup the relationships this way:

class Publication < ActiveRecord::Base   has_many :citations   has_many :cited_publications, :through => :citations, :source => :reference   has_many :references, :foreign_key => 'reference_id', :class_name => 'Citation'   has_many :refered_publications, :through => :references, :source => :publication end  class Citation < ActiveRecord::Base   belongs_to :publication   belongs_to :reference, :class_name => 'Publication' end  class Article < Publication end  class Book < Publication end  class Chapter < Publication end 

Now we can create the DB and try it out from the console:

$ rake db:migrate $ script/console  Loading development environment (Rails 2.2.2) >> a = Article.create!(:name => 'Article') => #<Article id: 1, ...> >> b = Book.create!(:name => 'Book') => #<Book id: 2, ...> >> a.citations.create(:reference => b) => #<Citation id: 1, publication_id: 1, reference_id: 2, created_at: '2009-02-15 14:13:15', updated_at: '2009-02-15 14:13:15'> >> a.citations => [#<Citation id: 1, ...>] >> a.references => [] >> b.citations => [] >> b.references => [#<Citation id: 1, publication_id: 1, reference_id: 2, created_at: '2009-02-15 14:13:15', updated_at: '2009-02-15 14:13:15'>]     >> a.cited_publications => [#<Book id: 2, type: 'Book', name: 'Book', created_at: '2009-02-15 14:11:00', updated_at: '2009-02-15 14:11:00'>] >> a.refered_publications => [] >> b.cited_publications => [] >> b.refered_publications => [#<Article id: 1, type: 'Article', name: 'Article', created_at: '2009-02-15 14:10:51', updated_at: '2009-02-15 14:10:51'>]