Quality improvement in switching-system software

The paper describes the effects on switching system software quality of development and maintenance activities. The effect of the application of object oriented methods and quantitative quality control methods in the development of switching system programs is evaluated by comparing the number of errors after shipping to that of earlier systems. Effective approaches to further improving the quality have been developed by analyzing error data obtained during development and maintenance. The main findings are as follows. (1) Although the error density in switching programs, which include call processing and system management functions, is the same as that in maintenance programs, errors in the switching programs are more likely to have a serious impact on the system when the errors are not discovered. Thus, quality control management that takes the potential impact of errors into account will more effectively improve the total software quality. (2) To increase the error detection rate in each testing phase, the omission of test items must be prevented by managing the correspondence of test items between each testing phase, and by supporting the generation of test items from the system specifications.