The figure below depicts the relationship among Product, Service, and Resource domain business entities.<br/>Business entities in the Product domain have a close relationship with business entities in the Service and Resource domains.  <br/>While Product business entities represent what the market sees of a provider’s offerings, Service and Resource business entities represent the realization of the offerings from a provider’s perspective. <br/>For example, a Broadband Internet ProductOffering is realized by two Services, one is a bandwidth connectivity service to the provider’s network; the second is a virtual connectivity service to the Internet Service Provider.<br/>Each ProductSpecification may be derived from CustomerFacingServiceSpecifications, or realized as StockItems or realized as ProductSpecifications proposed by Suppliers.<br/>The relation between ProductSpecification and StockItems only concerns tangible products such as Box (represented as a CompoundResourceSpec -Physical and Logical-) or such as a PSTN phone.<br/>The relation between ProductSpecification and CustomerFacingServiceSpecification concerns non-tangible products such as mobile line, call forwarding…<br/>And the relation between ProductSpecification and ProductSpecification proposed by Suppliers (through ProdSpecBPProdSpecChoice) concerns tangible or non-tangible products that we can buy to a Supplier.<br/>If it corresponds to a tangible goods it will be shipped directly to the customer by the supplier.<br/>