Kuniyuki Kikuchi

Widely-distributed train-traffic computer control system and its step-by-step construction

In a large scale mission critical real time control system, such as the Tokyo metropolitan area train traffic system, it is very difficult to construct the entire system at once. Moreover economic considerations makes year by year investment inevitable for developing the system. The new Tokyo metropolitan area train traffic computer control system, supplying service to 19 train lines, 300 stations and 6200 trains per day, has been constructed step by step over 8 years without halting train operations. Here the computer system is required to be expandable online during system operation and without disrupting already constructed subsystems. To enable testing during system operation, an autonomous decentralized online expansion technique is proposed. Then the effectiveness of the technique is demonstrated in a real system.<<ETX>>

Distributed management for software maintenance in a wide-area railway system

In a large scale real time control system, functions of subsystems differ slightly although they seem to be identical. Functions change when hardware is replaced or when the function itself is upgraded. If the standard system is generated by merging the differences and is installed then to each subsystem, subsystems become different with maintenance being carried out in each subsystem to fit its operational conditions. Furthermore, subsystems are distributed in a wide area. Software maintenance therefore becomes very difficult. The paper describes a distributed management for software maintenance in the Tokyo metropolitan area railway system. This management has two phases: generating programs for making maintenance easy and executing programs for increasing the reliability of the system. There it contributes to the effectiveness of maintenance and increases the reliability of the total system.