Widely distributed systems are constructed step-bystep over a long time. These systems must permit online testing. On-line testing verifies newly added application software by receiving the real data in the real environment without disrupting the operating subsystems. To enable testing during system operation, a n on-line test technique based on autonomous decentralized syst e m structure was proposed. In this paper, the functions t o verify various types of application software are proposed: (1) f o r non-real-time application software, checking whether it communicates with every operating application software. (2) f o r real-time application software, checking whether timing of output data is within the timing-deadline or not. (3) f o r n e w version software, verifying whether the version of all functions is newer than that of functions in the present software. An ezample of application software applied t o the online test and the effectiveness of the technique is shown in a real system.

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Widely distributed systems are constructed step-by-step over a long time. These systems are obliged critical timing check as a final test of newly added or modified real-time application programs in real environment. We propose an autonomous decentralized on-line test technique for verifying distributed and real-time control application programs. It enables testing during system operation without disturbing the operation. And it takes into consideration the difference of timing in on-line subsystems and test subsystem for the more precise verification. We apply the proposed technique to a validation tool for real distributed train traffic control systems and show its effectiveness.