Circuit-switched networks of video users with different grades of service are considered. The authors consider admission control schemes that result in an increase to network throughput at the expense of some fraction of the information (rate) transmitted by the video sources being dropped. The end-to-end probability of blocking video requests and the associated probability of rate dropping of video sources are evaluated along each network path for the above control schemes and for an arbitrary circuit-switched network architecture. Instead of the exact expressions, which require prohibitive computational effort, the stochastic knapsack approximation and the Monte Carlo summation method are employed.>

A revision is presented of E.B. Swanson's classification scheme for software maintenance (1976). The proposed classification system can be objectively determined from the changes that occur between versions of the software. The system was developed by analyzing the changes that occur between different versions of COBOL programs that were produced in commercial environments.>