Bull Hn Information Systems, Inc.

Andrew Y Pan

Charles P Ryan

Thomas H Howell

David W Rolston

A diagnostic expert system incorporating a cause-effect graph is disclosed in which 'yes', 'no' and 'unknown' are valid possible responses to a query. Each node in the graph is assigned a local decision factor (LDF) based on a given node's desirability for selection during best-first search and a collapsed decision factor (CDF) based on the average values of the LDFs for all its daughter nodes. For a current node being processed, a list of all its daughter nodes is obtained and examined to remove all daughter nodes that have been visited before in the current transition and all daughter nodes which have prerequisites that are not met. Then, the daughter node with the largest LDF is selected and its test function is executed. If the user response is 'yes', the daughter node is made the current node, and a list of its daughter nodes is obtained to continue the process. If the user response is 'no', the daughter node is added to the closed list, and the process continues with the next daughter node of the current node. If the user respoanse is 'unknown', the daughter node's CDF is compared with the LDFs for the other daughter nodes of the current node which are not on the closed list and which have their prerequisites met. If the CDF is larger than all the LDFs, the daughter node is made the current node to continue the process; otherwise, the daughter node with the largest LDF is selected, and its test function is executed to continue the process.

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Phoenix, AZ, United States of America

Andrew Y Pan