Expert system apparatus and methods

• US 4,916,633 A
• Filed: 03/24/1987
• Issued: 04/10/1990
• Est. Priority Date: 08/16/1985
• Status: Expired due to Fees

• Current Assignee: Wang Laboratories Incorporated
• Original Assignee: Wang Laboratories Incorporated
• Inventors: Bolling, Richard W., Tychonievich, Louis P.
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US07/030,250
• Time in Patent Office: 1,113 Days
• Field of Search: 364/200, 364/417, 364/513, 364/900
• US Class Current: 706/60
• CPC Class Codes: G06N 5/022 Knowledge engineering; Knowledge acquisition
• CPC Class Codes: G06N 5/045 Explanation of inference; Explainable artificial intelligence [XAI]; Interpretable artificial intelligence

Abstract

An expert system shell and expert systems created thereby. The expert system shell creates a knowledge base consisting of terms and their definitions, the definitions making up a hierarchy of definitions in which each definition depends only on definitions at lower levels in the hierarchy or on values obtained from sources external to the knowledge base. The expert system shell creates the knowledge base by asking the expert to define a given term and then asking him to define all undefined terms which appear in the definition of the given term. Because the hierarchy is created in this fashion, the definitions are guaranteed to be complete and non-contradictory. Expert systems created using the expert system shell employ an inferencing engine which determines the value of a given term by evaluating its definition. In the course of the evaluation, the definitions of terms required to define the given term are evaluated and external values required for the evaluation of the definitions are obtained. Users of the expert system may inquire of the system why it is seeking a given external value and how it obtained the results it did.

Claims

1. A digital computer system operable as an expert system, said computer system comprising:

storage means to store a knowledge base including hierarchically-defined terms and their definitions, the corresponding definition of each term defining its respective term using the value of one or more terms, each of whose definitions is at a lower level of the hierarchy, and/or using one or more external values external to the knowledge base; and

processing means for receiving commands from a user of the system, for producing inference commands in response to said user commands, for interrogating said storage means in response to said commands to obtain the definition of a given term, and for computing the value of said given term from its corresponding definition by obtaining the value of any term and any external value in the corresponding definition,

said system employing said computed value to produce an expert response to said user.

2. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

the definition of a term further includes a plurality of operators for defining how the value of a term and/or an external value is to be used in the definition; and

the processing means computes the value of said given term using the operators in the corresponding definition.

3. The digital computer system operable as an expert system as set forth in claim 2 and wherein:

the value of a term or an external value may be of the Boolean, arithmetic, or string types; and

the operators include a Boolean operator for operating on a Boolean value, an arithmetic operator for operating on an arithmetic value, and a text concatenation operator for operating on string values.

4. The digital computer system operable as an expert system as set forth in claim 3 and wherein:

the operators further include a case operator for associating each value in a list of values with a Boolean expression and returning the first value in the list whose Boolean expression has the value "TRUE" as the value produced by the operator.

5. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

each definition corresponding to a term is a function definition; and

the processing means computes the value of said given term by executing the function defined by the corresponding function definition.

6. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

the corresponding definition specifies the source of any external value used therein; and

the processing means obtains the value of any external value from the specified source.

7. The digital computer system operable as an expert system as set forth in claim 6 and wherein:

the storage means additionally includes a file and/or data base for storing values separate from knowledge base; and

the processing means being capable of obtaining the value of the external value from the file and/or data base.

8. The digital computer system operable as an expert system as set forth in claim 6 and wherein:

the digital computer system further comprises interactive input/output means coupled to the processor means for providing output information to and receiving input information from a user of the digital computer system; and

the specified source is the interactive input/output means and the specification of the source includes a specification of output information output to the interactive means.

9. The digital computer system operable as an expert system as set forth in claim 8 and wherein:

the specification of the output information includes a specification of a list of values; and

the user specifies the external value by selecting one of the values on the list of values.

10. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

the user commands include a user command which specifies the given term and to which the processing means responds by producing the computed value as the expert response.

11. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

the user commands include a user command specifying the given term to which the processing means responds by producing an expert response derived from the definition which shows how the current value of the given term was computed using the corresponding definition.

12. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

the user commands include a user command specifying the given term and an external value to which the processing means responds by using the specified external value to compute the computed value.

13. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

the digital computer system further comprises interactive input/output means employed by the user to receive a request for a user command, a request for an external value, and the expert response from the digital computer system and to provide the user commands and the external value to the digital computer system; and

the user commands include a user command provided on the input/output means in responnse to the request for the external value to which the processor means responds by producing an expert response from the definition which shows why the external value is required for the computation.

14. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

the storage means further includes means for retaining any external value used to produce the computed value; and

the user commands include a user command for altering one or more of the retained external values.

15. The digital computer system operable as an expert system as set forth in claim 14 and wherein:

the user command for altering one or more of the retained external values clears all of the retained external values.

16. The digital computer system operable as an expert system as set forth in claim 14 and wherein:

the user command for altering one or more of the value sets a specified one thereof to a new value specified in the user command.

17. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

the user commands include a user command for specifying a new term to which the processing means responds by receiving input from the user as required to produce a definition in the knowledge base corresponding to the new term and definitions for any undefined terms required for the corresponding definition until there are no undefined terms remaining in the corresponding definition.

18. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

the user commands include a user command for removing a term to which the processing means responds by removing the term and its definition from the knowledge base.

19. The digital computer system operable as an expert system as set forth in claim 1 and wherein:

the user commands include a user command for redefining a term to which the processing means responds by removing the definition for the term from the knowledge base and producing a new definition in the knowledge base corresponding to the redefined term and definitions for any undefined terms required for the new definition until there are no undefined terms remaining in the new definition.

20. The digital computer system operable as an expert system as set forth in claim 17 and wherein:

each corresponding definition is a definition of a function executable by the processing means and

the processing means computes the value of the given term by executing the function defined in the corresponding definition.

21. A digital computer system operable to define a given term for an expert system by creating a hierarchical definition of the given term for storage with the term in a knowledge base employed in the expert system comprising:

storage means for storing the knowledge base;

interactive input/output means for providing output information to and receiving input information from a user of the digital computer system who is the source of the definition; and

processing means coupled to the storage means and to the interactive input/output means for receiving the input information and providing the output information and receiving previously-defined terms and definitions and providing the given term and the definition created therefor and for responding to the given term received in the input information by providing output information requesting a description of the given term from the user, receiving input information containing the description from the user, analyzing the description to determine whether there is any term therein which does not have a definition in the knowledge base, and if there is not, ending the analysis, forming the definition for the given term from the description and the definitions of the previously-defined terms used therein, and storing the given term and the definition in the knowledge base, and if there is, providing output information requesting a description of the undefined term from the user and proceeding as for the given term, and continuing thus until no undefined term remains in the description of the given term or in any descriptions requested in the course of defining the given term.

22. The digital computer system as set forth in claim 21 and wherein:

each defined term represents a value;

the description of the defined term describes how the represented value is to be computed by the processing means; and

the definition of a given defined term is interpretable by the processing means to compute the value presently represented by the defined term.

23. The digital computer system as set forth in claim 22 and wherein:

each defined term is a function name;

the definition for the defined term is the function definition for the function name; and

the processing means determines the present value of the defined term by executing the function defined by the function definition.

24. The digital computer system as set forth in claim 22 and wherein:

the value of the defined term is computed using an external value external to the knowledge base;

the defined term'"'"'s description includes a first specification of the source of the external value; and

the defined term'"'"'s definition includes a second specification of the source of the external value which is interpetable by the processing means to obtain the external value from the specified source.

25. The digital computer system as set forth in claim 22 and wherein:

the description of a term describes how the value of the term is to be computed by means of specifications of one or more operators;

the definition of a term further includes operators corresponding to the specifications in the description; and

the processing means computes the value of said given term using the operators in the corresponding definition.

26. The digital computer system as set forth in claim 25 and wherein:

the value of a term may be of the Boolean, arithmetic, or string types; and

the operators include a Boolean operator for operating on a Boolean value, an arithmetic operator for operating on an arithmetic value, and a text concatenation operator for operating on string values.

27. The digital computer system as set forth in claim 26 and wherein:

the operators further include a case operator for associating each value in a list of values with a Boolean expression and returning the first value in the list whose Boolean expression has the value "TRUE" as the value produced by the operator.

28. The digital computer system as set forth in claim 24 and wherein:

the storage means additionally includes a file and/or data base for storing values separate from knowledge base; and

the processing means being capable of obtaining the value of the external value from the file and/or data base.

29. The digital computer system as set forth in claim 24 and wherein:

the specified source is the interactive input/output means and

the specification of the source includes a specification of output information output to the interactive means.

30. The digital computer system as set forth in claim 29 and wherein:

the specification of the output information includes a specification of a list of values; and

the user specifies the external value by selecting one of the values on the list of values.

31. The digital computer system as set forth in claim 21 and wherein:

the processing means creates the hierarchical definition in response to input information specifying the given term and that the given term be defined.

32. The digital computer system as set forth in claim 21 and wherein:

the processing means removes a previously-defined term and corresponding hierarchical definition from the knowledge base in response to input information specifying the previously-defined term and that the previously-defined term be removed from the knowledge base.

33. The digital computer system as set forth in claim 21 and wherein:

the processing means replaces the corresponding hierarchical definition for a previously-defined term with a new definition in response to input information specifying the previously-defined term and that the previously-defined term is to be redefined.