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A security kernel is a software and hardware mechanism that enforces access controls within a computer system. The correctness of a security kernel on a PDP-11/45 is being proved. This paper describes the technique used to carry out the first step of the proof: validating a formal specification of the program with respect to axioms for a secure system. [ABSTRACT FROM AUTHOR]

The article introduces the topics dealt in the October 1997 issue of the journal "Communication of the ACM." As technologies and technical abilities evolve, so does the need for moving system architectures in the same direction. Easier said than done, since it's exceedingly difficult to create structures that can be upgraded, updated, or upended at every advancing step along the way. Therein lies the beauty of object-oriented application frameworks, a promising technology for reusing existing software designs to improve quality and cut costs. This month's special section focuses on the modular, reusable, and customizable features of frameworks technology. Their advantages are examined via real-life applications from experienced authors drawn into this project by Guest Editors Mohamed Fayad and Doug Schmidt. The articles detail the design principles underlying object oriented frameworks through a variety of applications. They illustrate economical face-lifts for classic architectures, and indicate the considerable role frameworks play in contemporary software development. Other articles in this issue touch on an eclectic array of topics. For instance, the possibilities of a computer-based immune system that could provide viral protection much like a biological system is the focus of a fascinating discussion.