added relation_type and work_type classes. #130

app/models/relation_type.rb

@@ -0,0 +1,3 @@
+class RelationType < ActiveRecord::Base
+
+end

app/models/work.rb

@@ -12,6 +12,7 @@ class Work < ActiveRecord::Base
   include Resolvable
 
   belongs_to :publisher, primary_key: :crossref_id
+  belongs_to :work_type
   has_many :retrieval_statuses, :dependent => :destroy
   has_many :sources, :through => :retrieval_statuses
   has_many :alerts

app/models/work_type.rb

@@ -0,0 +1,3 @@
+class WorkType < ActiveRecord::Base
+  has_many :works
+end