A help desk hinges on the concept of call, meant as a contact made by a customer to report a problem or e bought. The help-desk service includes a front-end where operators take the customer calls, and a back-end where some experts try to solve the problems. The customer opens the contact by calling the front-end. If possible, the front-end directly manages the problem and gives a solution to the customer, otherwise he hands the problem to an expert. During its lifetime, a call can be overtaken by different persons and groups, but in the end its solution will always be communicated to the customer by a front-end operator. Every activity carried out during a call gives rise to a call detail, so the story of a call can be reconstructed by orderly browsing its details. The problems managed by the help desk are classified into a recursive subject hierarchy. CUSTOMERS_DB For every customer, the department where he works and the one he bills to are distinguished. CONTRACT CUSTOMER COMPANY *ContractCode *CustomerCode Price *Company Code of Agent FirstName Name LastName StartDate Address Address EndDate city city Type includes works in CITY *CityCode Name state DEPARTMENT * Company Code *Dept Code Name Address City Manager -bills to