The following figure gives an overview of the relationships between Product, Service and Resource Specifications<br/>A ProductOffering represents how the ProductSpecification is sold (i.e. packaging rules, prices, alterations, commitments…).<br/>The ProductSpecification represents a product specification as perceived by the business user and specifies what the marketing operator wants to sell at a functional level (i.e. what are the capacities, which usages are available…).<br/>It can represent:<br/>        • tangible goods (Terminal, phone, mobile, fax, modem)<br/>        • or intangible goods (like an Anti-Spam service for email).<br/>When the ProductSpecification represents a tangible goods, it is realized as ResourceSpecification. Corresponding Resources are stored in warehouses or bought to a supplier on demand.<br/>When the ProductSpecification is an intangible good, it is either realized as a CustomerFacingService (when the Service Provider is able to realize it) or bought as a ProductSpecification proposed by a Supplier (when the Service Provider is not able to realize it). For example, a Broadband know-how might be built or bought depending on the location of it.<br/>The CustomerFacingServiceSpec represents all the Service Provider’s know-how of intangible goods at a functional level. It would be more appropriate to name it KonwHowSpec or ProductFacingServiceSpec, but the name is not changed as it is well known.<br/>The ProductSpecification corresponds to a sub-set of the Service Provider’s know-how according to what marketing people want to sell. Therefore, a ProductSpecification is a restriction of CustomerFacingServiceSpecs.<br/>When the ProductSpecification corresponds to a tangible good, then it is realized as a ResourceSpecification.<br/>The ResourceFacingServiceSpec represents the technical solutions that the Service Provider can implement for CustomerFacingServiceSpec.<br/>Each technical solution (ResourceFacingServiceSpec) requires ResourceSpecifications to be realized and might require buying part of the solution to a supplier (for example the Service Provider might have to buy the Local Loop to provide a broadband access).<br/>Not presented in the diagram: Sometimes the company is not able to realize the ProductSpecification on its own; in these cases, they will have to buy all or part of the technical solution. This is the case for MVNOs that always have to buy what they sell from a Supplier.<br/>