PURPOSE: To prevent the reduction of processing speed by prohibiting checking for debugging when an expert system constructing shell is actually being used.

CONSTITUTION: The list data file of function names for debugging is provided on an expert system construction shell and, when the shell is actually used, the list data file is loaded and the coincidence between the function name in there and the function name in the list data is detected from the next file. Then the remaining section except the coincident function name part is loaded. Since the debugged section is not loaded at the time of actual use, the processing speed is not reduced and a memory is not used wastefully when an expert system is executed.