Diagnosis of Multiple Faults in a Nationwide Communications Network

Abstract

The Network Diagnostic System (NDS) is an ARBY based expert system for fault isolation in a nationwide communi c ations network (COMNET). Due to both the structure and function of the network, failures in COMNET are often multiple component failures (either dependent or independent) or intermittent failures. The maintenance procedure for isolating and correcting faults in COMNET exploits multiple types of know ledge, including the topological structure of COMNET , geographic organiza tion, and frequency of failure information. Using ARBY, fault isolation in NDS is represented as a heuristic search through a space of hypotheses. The available diagnostic tests impose a refinement hierarchy on the space of hypotheses , enabling the exploitation of hierarchical search . Back links to more general hypotheses at higher levels in the refinement hierarchy are introduced to ensure the isolation and repair of multiple and intermittent failures. The NDS currently perf or ms at the level of an intermedia te COMNET diagnostician.