Cover story has been a controversial concept for the last 20 years. This concept was first introduced in 1991 in the SEAVIEW project [4] as an explanation for the polyinstantiation technique used in multilevel databases, i.e., databases which support a multilevel security policy. To illustrate the concept of polyinstantiation, consider the example of multilevel relational database that contains the relation EMPLOYEE as shown in Table 1. This relation stores the salary of each employee of some organization. The additional attribute called "Tuple_class" represents the classification level assigned to each tuple in relation EMPLOYEE. To get an access to this multilevel relation, each user receives a clearance level.