Catalog Object model is the biggest one in VCF. The main entities you will most likely to work with are Catalog and Item. This object model is divided into several parts for clarity and simplicity. These diagrams should help in better understanding of entity relations, class inheritance and characteristics.
Catalog class diagram
The main features of catalogs and categories.
Item class diagram
The main features of items (goods).
Property class diagram
The detailed features of properties (metadata) and their concrete values (data).