mycin provided by: sharif university students modified: vali derhami

MYCINMYCINProvided by: Sharif university StudentsModified: Vali Derhami

Table of ContentsTable of Contents

What’s the Problem?Why an Expert System?What’s MYCIN?Major FeaturesProblem Solving ApproachOther MYCINsSummary

What’s the Problem?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?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?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?What’s MYCIN?

A rule-based expert system

Developed at Stanford University – 1976

Uses backward chaining for reasoningPerforms depth first, exhaustive search of all

rules.Incorporates about 500 rules

Written in INTERLISP (a dialect of LISP)

Major FeaturesMajor Features

Using Backward Chaining

Separate Knowledge from Control

Incorporates Meta-Rules

Inexact Reasoning

Remember Prior Sessions

Accommodates the User

Major Features, Major Features, Backward ChainingBackward 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 negativeAND the morphology of the organism is rodAND the aerobicity of the organism is anaerobicTHEN

there is strongly evidence (0.8) that class of the organism is enterobacteriaceae

Major Features,Major Features,Separate knowledge & controlSeparate knowledge & control

Advantages

Easy to add new knowledge

Easy to modify existing knowledge

Major Features,Major Features,Incorporates Meta-RulesIncorporates Meta-Rules

To enable the system to redirect its search

IF the infection is a pelvic-abscessAND there are rules that mention in their premise enterobacteriaceae AND there are rules that mention in their premise gram positive rodsTHEN 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,Major Features, Inexact ReasoningInexact 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,Major Features, Inexact ReasoningInexact 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,Major Features, Remember Prior SessionsRemember 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,Major Features, Accommodates the UserAccommodates 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


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.


Provide Explanation

MYCIN can ◦ Explain why it’s asking a question

◦ Explain how it derived a conclusion

◦ Explain why it found other result implausible


Provide Explanation , why

System : How old is the car’s battery?User : WHY?System : This will aid in determining the battery’s condition :

RULE 037IF The car battery’s age is over five yearsAND The car battery’s voltage is below 10 voltsTHEN The battery’s condition is probably bad


Provide Explanation , 2nd why

User : WHY?System : This will aid in determining the proper recommendation

RULE 044IF The battery’s condition is probably bad THEN Recommend replacing the battery


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 044IF The battery’s condition is probably bad THEN Recommend replacing the battery

I use Rule 037 to conclude the conditions of the batteryRULE 037IF The car battery’s age is over five yearsAND The car battery’s voltage is below 10 voltsTHEN The battery’s condition is probably bad

You told me :1. The car battery’s age is over five years2. The car battery’s voltage is bellow 10 volts


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,Major Features, SummarySummary

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 ApproachProblem 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 , DiagnosisProblem 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


Classification approach

Gram

Identify

AerobicityMorphology

Other rules

Other rules


Inexact Diagnosis◦ Certainty factor propagation

Incrementally acquired evidence

CFold + CFnew (1- CFold ) CFold , CFnew > 0

CFrevised = CFold + CFnew (1+ CFold ) CFold , CFnew < 0

(CFold + CFnew )/(1- min{|CFold |,| CFnew|}) CFold .CFnew < 0

Depth First Search◦ Series of questions◦ Natural interaction

Problem Solving Approach , Problem Solving Approach , PrescriptionPrescription

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

Plan TestGenerateOutput


Plan◦ Potentially effective drugs for each suspected organisms

Organism-1 Orgnaism-2 Organism-3--------------------------------------------------------------------------------Rank-1 Drug-A Drug-B Drug-CRank-2 Drug-D Drug-A Drug-ERank-3 Drug-C Drug-C Drug-F-------------------------------------------------------------------------------


Generate◦ Procedural task◦ Generating all possible recommendations◦ All recommendations should eliminate all infecting organisms

Drug Prescription 1: Drug-CDrug Prescription 2: Drug-A and Drug-E...


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 Rank3-----------------------------------------------------------------------------------

1 1 0 0 2 2 0 0

3 1 1 0 .

.Recommend his best recommendation to the physician

Sample MYCIN Session

1. Patient’s name: (first - last) UPENDRA HAGWAT .

2. sex: ** M

3. Age: ** 55

4. 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 - 1 - - -

5. 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 - 1 - - -

7. 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 - 1 - - -

23. 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 MYCINsOther 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

SummarySummary

Knowledge is PowerEasy modification of knowledge baseSeparate knowledge from controlInexact reasoningAccommodate the userMeta-rulesReport immediate important resultsOnly recommend the user!

mycin provided by: sharif university students modified: vali derhami

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