MYCIN Provided by: Sharif university Students Modified: Vali Derhami

Table of Contents What’s the Problem? Why an Expert System? What’s MYCIN? Major Features Problem Solving Approach Other MYCINs Summary

What’s the Problem? Diagnosing and treating patients with infectious blood diseases ◦Difficulties  Time Consuming  Misuse and overuse of antibiotics  Shortage of expertise  System to help physicians

Why an Expert System? An expert was required to solve the problem. Experts on the problem were scarce or unavailable because of time constraints. Immediate expertise was needed in a possibly life treating situation. Time constraints required decisions to be made with limited or inexact information

Why an Expert System? The computer solution needed to be accommodating to the user, who may have limited experience with computers. Existing solutions may be irrational in cases where drug recommendations were inappropriate for the problem. Remembering the appropriateness and possible contradictions of a large number of drugs was a challenge for the physician.

What’s MYCIN? A rule-based expert system Developed at Stanford University – 1976 Uses backward chaining for reasoning Performs depth first, exhaustive search of all rules. Incorporates about 500 rules Written in INTERLISP (a dialect of LISP)

Major Features Using Backward Chaining Separate Knowledge from Control Incorporates Meta-Rules Inexact Reasoning Remember Prior Sessions Accommodates the User

Major Features, Backward Chaining To identify the nature of infection ( تشخیص عفونت ) To form a suggested therapeutic remedy ( راه درمان ) IF the stain of the organism is gram negative AND the morphology of the organism is rod AND the aerobicity of the organism is anaerobic THEN there is strongly evidence (0.8) that class of the organism is enterobacteriaceae

Major Features, Separate knowledge & control Advantages  Easy to add new knowledge  Easy to modify existing knowledge

Major Features, Incorporates Meta-Rules To enable the system to redirect its search IF the infection is a pelvic-abscess AND there are rules that mention in their premise enterobacteriaceae AND there are rules that mention in their premise gram positive rods THEN there is suggestive evidence that rules dealing with enterobacteriaceae should be evoked before those dealing with gram positive rods. More closely follow human problem solving.

Major Features, Inexact Reasoning To work with incomplete data To make decision under life-treating constraint of limited time. UNKNOWN information as input Certainty factor[-1,+1] for uncertain information Certainty factor for inexact rules: IF Evidence THEN Conclusion CF 0.7

Major Features, Inexact Reasoning To be able to derive solutions under these conditions : ◦UNKNOWN inputs ◦UNCERTAIN inputs ◦UNEXACT rules Solutions that are not completely precise but like those determined by human expert, usually acceptable.

Major Features, Remember Prior Sessions Remembers information from prior session: ◦Data provided to MYCIN ◦Conclusion drawn by MYCIN ◦Findings of MYCIN (invading organisms, etc.) When new information become available later MYCIN can correct it’s mistake like human expert

Major Features, Accommodates the User For an expert system to be accepted by users (in MYCIN domain, physician), it should be accommodating To perform the function of the expert in acceptable manner, MYCIN had to be easy to use and present itself in manner that was natural to the physician. ◦Natural Language Interaction ◦Spelling Checker ◦Provide Explanation ◦Provide Alternative Recommendation

Major Features, Accommodates the User Spelling Checker What a program can do when miss-spell occurred? ◦Fatal error : 6B4A program aborted ◦Invalid response, please retype. ◦Some better way! MYCIN uses “DID YOU MEAN …” ◦Choose nearest answer from list of acceptable answers of a question.

Major Features, Accommodates the User Provide Explanation MYCIN can ◦Explain why it’s asking a question ◦Explain how it derived a conclusion ◦Explain why it found other result implausible

Major Features, Accommodates the User Provide Explanation, why System : How old is the car’s battery? User : WHY? System : This will aid in determining the battery’s condition : RULE 037 IF The car battery’s age is over five years ANDThe car battery’s voltage is below 10 volts THEN The battery’s condition is probably bad

Major Features, Accommodates the User Provide Explanation, 2 nd why User : WHY? System : This will aid in determining the proper recommendation RULE 044 IF The battery’s condition is probably bad THENRecommend replacing the battery

Major Features, Accommodates the User Provide Explanation, how System : I recommend that you replace the battery, User : HOW? System: I used Rule 044 to conclude that the recommendation is to replace the battery RULE 044 IF The battery’s condition is probably bad THENRecommend replacing the battery I use Rule 037 to conclude the conditions of the battery RULE 037 IF The car battery’s age is over five years ANDThe car battery’s voltage is below 10 volts THEN The battery’s condition is probably bad You told me : 1. The car battery’s age is over five years 2. The car battery’s voltage is bellow 10 volts

Major Features, Accommodates the User Provide Alternative Recommendation Wanted the physician to feel in control and have the final say on the subject Recommend the physician list of drugs Can use alternative

Major Features, Summary Contain Knowledge Easy modifiable knowledge Using backward chaining Using Meta-rules to control search Conducts session in English Perform inexact reasoning Remember prior session Explain why a question is being asked Explain how a result was obtained Explain why a result was not obtained Provide alternative solutions if requested

Problem Solving Approach Phase1:Diagnosis  What is the nature of infection?  What organisms are causing the infection? Phase2: Prescription  What drugs should eliminate the infecting organism?  What drugs should be safe for the patient?

Problem Solving Approach, Diagnosis General background information on the patient Available result from laboratory tests Direct questioning toward suspected infection ◦Intelligent sequence of questions ◦A sense of credibility for the program in mind of the physician Ask physician about his guess about the infection before program identification ◦Avoid unnecessary search ◦A cooperative style of interaction

Problem Solving Approach, Diagnosis Classification approach Gram Identify AerobicityMorphology Other rules

Problem Solving Approach, Diagnosis Inexact Diagnosis ◦Certainty factor propagation  Incrementally acquired evidence CF old + CF new (1- CF old ) CF old, CF new > 0 CF revised = CF old + CF new (1+ CF old ) CF old, CF new < 0 (CF old + CF new )/(1- min{|CF old |,| CF new |}) CF old.CF new < 0 Depth First Search ◦Series of questions ◦Natural interaction

Problem Solving Approach, Prescription Prescription must ◦Eliminate the suspected infection organisms ◦Minimize the number of recommended drugs ◦Be safe for the patient  Combination of drugs  General conditions of patient Using plan-generate-test method PlanTestGenerate Output

Problem Solving Approach, Prescription Plan ◦Potentially effective drugs for each suspected organisms Organism-1 Orgnaism-2 Organism Rank-1 Drug-A Drug-B Drug-C Rank-2 Drug-D Drug-A Drug-E Rank-3 Drug-C Drug-C Drug-F

Problem Solving Approach, Prescription Generate ◦Procedural task ◦Generating all possible recommendations ◦All recommendations should eliminate all infecting organisms Drug Prescription 1: Drug-C Drug Prescription 2: Drug-A and Drug-E.

Problem Solving Approach, Prescription Test ◦Recommendation should not have 2 drugs from the same drug class ◦Drugs with higher rank has higher priority ◦Drugs should be safe for the patient Number of drugs from each rank Instruction Rank1 Rank2 Rank Recommend his best recommendation to the physician

Sample MYCIN Session 1. Patient’s name: (first - last) UPENDRA HAGWAT. 2. sex: ** M 3. Age: ** Are there any cultures for Upendra Hagwat which may be related to the present illness, and from which organisms have been grown successfully in the microbiology laboratory? ** Y CULTURE From what site was the specimen for CULTURE - 1 taken? ** BLOD = BLOOD 6. Please give the date and time when CULTURE-1 was obtained. (mo/da/yr time) ** JUN 20, 1977 The first organism isolated from the blood culture of 20- JUN-77 (CULTURE-1) will be referred to as:

- - - ORGANISM Enter the laboratory - reported identity of ORGANISM-1: ** UNKNOWN 8. The strain of ORGANISM-1: ** NEG (Preliminary lab results give some clues). 9. Is ORGANISM - 1 rod or coccus (etc.): ** ROD 10. What is the form of the individual organisms (e.g. lancet-shaped for cocci, fusiform for rods, etc)? ** FUSIFORM....

- - - ORGANISM What is the suspected portal of entry of the gramneg rod from the blood culture of 20-JUN- 77 (ORGANISM-1) into this site? ** GI (6) 24. Is Upendra Hagwat a burn patient? ** N 25. Is Fred Braun a compromised host (e.g. alcoholic, sickle-cell- disease, immunosuppressed)? ** N 25. Is Upendra Hagwat febrile? ** Y

RECOMMENDATION: 1 - colistin 2 - polymyxin 3 - gentamicin 4 - carbenicillin 5 - sulfisoxazole MYCIN selects drugs only on the basis of the identity of offending organisms.

Other MYCINs EMYCIN ◦Empty MYCIN ◦Large Amount of LISP Code TMYCIN ◦Tiny EMYCIN ◦Only some features of EMYCIN PUFF ◦Based on EMYCIN ◦Has knowledge of lung diseases NEOMYCIN ◦Base on MYCIN ◦For teaching, in the laboratories

Summary Knowledge is Power Easy modification of knowledge base Separate knowledge from control Inexact reasoning Accommodate the user Meta-rules Report immediate important results Only recommend the user!