A technique for technology evolution based on the χ window system

As Department of Defense budgets decrease, defense contractors need new techniques to upgrade existing fielded systems to new technology without incurring the expense of a total system replacement. In this paper, we describe the first in a multi-phased approach used at ESL to upgrade a large signal intelligence (SIGINT) system from a mainframe-based, FORTRAN and assembler application to a workstation-based Ada application. In this phase, much of the existing system was retained while significant new design concepts were introduced. The approach was driven by the need to keep tests at a minimum while accommodating new requirements, improving performance, and setting the stage for migration to totally new technology. A key to the upgrade approach was the use of the χ Window System. All of the workstations use χ for the graphical user interface and Ada for the applications code