Abstract: A computer system and method are used for managing product knowledge related to products offered for sale by a selling entity. The computer system includes a memory arrangement. At least one processing unit is coupled to the memory arrangement. A data model is defined that describes relationships between data categories. A data instance is input that corresponds to one or more of the data categories. The data instance represents at least part of the product knowledge. The computer system can also create a user-defined relationship item for the data instance and present the product knowledge to a user of the system in a manner established by the data model and the user-defined relationship. The product knowledge that is presented includes information that corresponds to the data instance.