I''m trying to understand how to do the following, but am finding myself stuck. I have three main tables; here are the first two: CREATE TABLE reference_items ( "id" integer primary key, "type" varchar(20), "title" varchar(255), "year" year(4) ); CREATE TABLE "agents" ( "id" integer primary key, "type" varchar(20), "sort_name" varchar(255), "description" text ); So I''ve got ReferenceItem and Agent classes, each of which has subclasses (for the first, stuff like Book, Article, etc.). The third key table links the above: CREATE TABLE contributors ( "reference_item_id" integer, "agent_id" integer, "position" integer, "type" varchar(20) ); The Contributor class currently has four subclasses: Author, Editor, Publisher, and Translator. So the idea is I need to be able to separely track the type and order of each class. So how do I get this correctly setup in my models? Or can I? Bruce