JPS62256128A - Inference system - Google Patents

Abstract

PURPOSE:To solve a compound problem such as trouble diagnosis including a restoration method and to build a multipurpose, high performance export system by executing the multistaged inference combined with backward inference and forward inference. CONSTITUTION:The titled system is provided with an inference part 1 to execute the forward inference, a backward inference part 2 to verify whether condition used by the forward inference part 1 holds or not, and a rule preservation part 3 to preserve rules in a IF-THEN format. The forward inference part 1 is composed of a presupposition preservation part 11 to preserve presupposition or the inference result just before the presupposition is obtained, a rule search part 12 to search rules that use the presupposition preserved in the presupposition preservation part 11 as one condition in a condition part out of the rule preservation part 3, and a rule execution part 13 to execute the searched rule, and a conclusion decision part 14 to decide whether the conclusion obtained through the execution is goal of inference.

Description

[Detailed Description of the Invention] [Objective of the Invention 1 (Field of Industrial Application) The present invention relates to an inference method such as an expert system that accumulates the knowledge of experts and uses this to support diagnosis, design, etc. .

(Prior Art) Conventional inference methods include forward inference methods and backward inference methods.

This forward inference method is a method that infers the conclusion that ``y is b'' based on the rule ``If X is a, then y is b'' and the fact that ``X is a.'' .

Also, the backward inference method is unrelated to the unknown hypothesis that wants to prove "y is b", and from the rule "If X is a, then y is b", "X is a" is established. This is a method of inferring the success or failure of a hypothesis by examining whether it is true or not.

When applying these inference methods as inference methods for expert systems, forward inference methods are said to be suitable for planning and design type expert systems, and backward inference methods are said to be suitable for diagnostic type expert systems. .

However, recently the scope of problems to be solved by inference has expanded, and it is no longer possible to simply decide, ``This problem is of such-and-such type, so I will adopt this inference method.'' Rather, it is often necessary to combine these two inference methods to perform inference that takes advantage of the characteristics of both.

For example, after diagnosing the failure of a machine, you can use the diagnosis results as a prerequisite to infer countermeasures for repair, or roughly use the countermeasures as a prerequisite to infer the types and quantities of necessary parts and tools. There are cases. In this case, it is desirable to perform fault diagnosis using backward reasoning, and then perform the fault diagnosis using forward reasoning.

In such a case, if you try to realize the above inference by combining the independent forward inference method and backward inference method, it will be difficult to unify the rule expressions, a large amount of development man-hours will be spent, and the overall inference will be The problem of poor processing efficiency was common.

(Means for solving the problem) Conventional inference methods often have the problem that the inference method is fixed and cannot be flexibly adapted to suit the application.

The present invention was made in response to this situation, and it is an object of the present invention to provide an inference method that can flexibly execute forward inference and backward inference.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention verifies the establishment of a hypothesis from the inference rules in an inference method in which inferences are made from preconditions and inference rules. A backward inference means and a forward inference means that performs inference from preconditions and inference rules are provided, multi-stage inference is performed while obtaining intermediate inference results at each stage, and the intermediate inference results up to a predetermined stage are retrospectively inferred by the backward inference means. Intermediate IW theory results at subsequent stages are obtained by forward reasoning using forward reasoning means.

(effect) Therefore, inference can be made as follows.

That is, first, a predetermined intermediate inference result is obtained while verifying a hypothesis by backward inference by the backward inference means.

Next, forward inference is executed by forward inference means using this intermediate inference result as a precondition.

Further, this intermediate inference result is regarded as a precondition for determining another goal, and forward inference is performed to perform multi-stage inference.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a 4G configuration of an inference device according to an embodiment of the present invention.

This inference device includes a forward inference unit 1 in which forward inference is executed, a backward inference unit 2 in which the success or failure of conditions used in the forward inference unit 1 is verified, and a rule storage unit in which rules in IF-THEN format are stored. It consists of Section 3.

Further, the forward inference section 1 stores a precondition storage section 11 in which the precondition or the previous inference result is stored, and a rule that sets the precondition stored in the precondition storage section 11 as one of the conditions in the condition section. It is composed of a rule execution unit 12 that searches the storage unit 3, a rule execution unit 13 that executes the searched rule, and a conclusion determination unit 14 that determines whether the conclusion obtained as a result of the execution is the target of the inference. ing.

Next, the operation of this inference device will be explained using FIG.

Figure 2 shows the failure diagnosis lW executed by this reasoning device.
FIG.

In this fault diagnosis, first the cause of the failure is identified, then a recovery method for the cause of the failure is determined, and materials necessary for this recovery method are also determined.

First, by assuming the cause of the failure, backward reasoning A is activated, and in order to verify the cause of the failure, evaluation of the success or failure of the event serving as the condition is repeated.

When the cause of the failure is identified by backward reasoning A through the above operations, the inference of a recovery method is then activated using this cause of failure as a precondition. The inference of this recovery method is advanced by forward inference B and backward inference C, which verifies conditions in the condition part of this forward inference B that are not known whether they are successful or not.

The identified cause of failure is stored in the prerequisite storage unit 11. Then, among the rules stored in the rule storage section 3, the rule search section 12 selects one whose condition part partially matches the stored failure cause.

Next, the selected rule is executed in the rule execution unit 13, but if an event other than the cause of the failure exists in the condition part of this rule, the backward reasoning unit 2 verifies whether this event is successful or not. be done.

When all the conditions in the conditional part are satisfied, the conclusion determining part 14 determines whether the conclusion of this rule is the recovery method that is the goal of this forward inference, and if it is the target recovery method, this recovery method is This is the conclusion of Inference B.

If it is not the target recovery method, the result of this forward inference is stored in the precondition storage unit 11, and the above operation is repeated.

As described above, a recovery method can be inferred from the cause of the failure.

Similarly, with this recovery method as a prerequisite, the necessary material inferences, ie, forward inference and backward inference E, can be continued.

[Effects of the Invention] As described above, according to the present invention, multi-stage inference that combines backward inference and forward inference can be performed, so complex problems such as failure diagnosis including recovery methods can be solved. It is possible to horizontally build a multi-purpose and high-performance expert system.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an inference device according to an embodiment of the present invention, and FIG. 2 is a diagram showing a fault diagnosis inference process executed by the embodiment. 1...Forward reasoning section 2...Backward reasoning Product applicant Toshiba Corporation Representative Patent attorney Sasu Suyama - Figure 1 Figure 2

Claims (4)

[Claims] (1) In an inference method that makes inferences from preconditions and inference rules, there is provided a backward inference means for verifying the establishment of a hypothesis from the inference rules, and a forward inference means for making inferences from the preconditions and the inference rules, An inference method characterized in that intermediate inference results up to a predetermined stage are obtained from backward inference by the backward inference means, and intermediate inference results at subsequent stages are obtained from forward inference by the forward inference means. (2) The inference method according to claim 1, wherein the forward inference means continues the forward inference using the intermediate inference result obtained by the immediately preceding forward inference as a precondition. (3) The forward inference means is configured to activate the backward inference means using this condition as a hypothesis when the condition in the condition part of the inference rule is not included in the prerequisites at the time of forward inference. reasoning method. (4) The inference method according to any one of claims 1 to 3, wherein the forward inference means is activated only by the immediately preceding intermediate inference result.