E.g. a installation which have the projekttype customer file with the field customer ID, you could find all the documents from a customer with the customer ID 42 really easy, if you would search for a Projekt with the type customer file and with the customer ID 42. In the located projekt are all documents from the customer with the customer ID 42. This require that the projekt excist and that the document from the certain customer were already added to the projekt. The grouping in the “customer file“ is class-independent. An other way to search all documents from the customer ID 42 is the spanning search.