SQL Developer

Dear All,

I have this database design where i have.

1 - A customers entity/table with cust_id & cust_type_id columns.
2 - A customer_types entity/table with cust_type_id & cust_type_name columns.
3 - A individual_customers entity/table with cust_id, cust_firstname. cust_lastname and annual_income columns.
4 - A company_customers entity/table with cust_id, company_name & CEO columns.

a - I have simplified the tables and excluded many columns.
b - The customers entity/table is a super type with respect to the individual_customers entity/table and company_customers entity/table with one to one relationship between them.
c - The type discriminator is the cust_type_id column.
d - The customer_types entity/table records types of customer (individual person, sole proprietorship,partnership, corporation, and so on)
e - The logical model is to be implemented in to a physical with a three-tables approach (as is).

Now In IDEF1X notation, the type is shown using a symbol that looks like a circlewith a line under it. Further more the relationaship is either disjoint or overlaping. How do I implement this design in Orcale SQL developer Data Modeler. I want to create a super type entity/table called customers and have two sub type entity/tables called individual_customers & company_customers. Some thing like this

http://i31.tinypic.com/14ipdol.jpg

I do not see any options in Oracle SQL Developer Data Modeler for super types & subtypes. Does this mean that it does not support inheritance (specialization & generalization) OR that I should just create all the required entities/tables and join them with one to one relationships with out stating that they are super & sub types.