Product list is the company’s personal list of products. In the case of the Seller, this list represents the products/services the company sells. From the Buyer’s side, this is a list of products that the company buys. The buyer’s product list consists of bundles of products that are called IPS (Interchangeable Product Set). This gives the Buyer the option to get offers for similar products when the company has no preferences for a certain type or model of the products. Visible for all Buyers is IPS Library which contains voluntary shared IPSs made by different Buyers. Both users can add products to their list by either searching for them in the Product Catalogue or by adding non-existing products to the Product Catalogue.