The primary goal of the compartmented mode workstation (CMW) project was to articulate the security requirements that workstations must meet to process highly classified intelligence data. As a basis for the validity of the requirements developed, a prototype was implemented which demonstrated that workstations could meet the requirements in an operationally useful manner while still remaining binary compatible with off-the-shelf software. The security requirements not only addressed traditional security concerns but also introduced concepts in areas such as labeling and the use of a trusted window management system. The CMW labeling paradigm is based on associating two types of security labels with objects: sensitivity levels and information labels. Sensitivity levels describe the levels at which objects must be protected. Information labels are used to prevent data over classification and also provide a mechanism for associating with data those markings that are required for accurate data labeling, but which play no role in access control decisions. The use of a trusted window manager allows users to easily operate at multiple sensitivity levels and provides a convenient mechanism for communicating security information to users in a relatively unobtrusive manner. Information labels are not used by reference monitor, permissions are referenced in Sensibility labels.