From the thesis abstract: "A design for a secure, multi-user, File Storage System is developed. This design, incorporating a concurrently developed Security Kernel, provides a multilevel secure f1exib1e file storage serving a distributed system of dissimilar computers. The Security Kernel is responsible for non-discretionary (e.g., classification and clearance) security and the File Storage System Supervisor is responsible for discretionary (e.g., 'need to know') security. Multilevel security is achieved by the controlled access to consolidated file storage by Host computer systems. Multiprogramming of surrogate Supervisor processes operating on behalf of the Host computer systems provides for system efficiency. A segmented memory at the Supervisor level allows controlled data sharing among authorized users. . System integrity is independent of the internal security controls (or lack of them) in the distributed systems; the File Storage System prevents system-wide security side effects. A loop free structure along with system simplicity and robustness are design characteristics."