Presentation

MYCIN Expert System

Presented by

Junaid KhanDepartment of Computer ScienceUniversity of Peshawar Pakistan

Junaid_upesh@yahoo.com

AI Continued…….☻Also, the problem-solving methods themselves are

usually qualitative reasoning techniques that relate items through judgmental rules, or heuristics, as well as through theoretical laws and definitions.

☻An algorithm is a procedure that is guaranteed either to find the correct solution to a problem in a finite time or to tell you there is no solution.

☻ For example, an algorithm for opening a safe. ☻Few problems in medicine have algorithmic

solutions that are both practical and valid.☻Physicians are forced to reason about an illness

using judgmental rules and empirical associations along with definitive truths of physiology.

What is MYCIN?☻MYCIN is an expert system (BruceBuchanan and

Shortliffe, 1983).☻By that we mean that it is an AI program designed (a) to provide expert-level solutions to complex

problems, (b) to be understandable, and (c) to be flexible enough to accommodate new knowledge easily. Because they have designed☻MYCIN to provide advice through a consultative

dialogue, we sometimes refer to it as a consultation system.

History of MYCIN☻ MYCIN was an outgrowth of DENDRAL .

☻ The MYCIN team members

Bruce Buchanan( Professor of Computer Science, Philosophy, and Medicine, with the Department of Computer Science at the University of Pittsburgh ).

Stanley Cohen, then Chief of Clinical Pharmacology at the Stanford University Medical School.

Edward Shortliffe(a physician and computer scientist at Stanford Medical School).

George Forsythe, then Chairman of the Computer Science Department.

Continued…..☻After six months of collaborative effort on

MEDIPHOR, their discussions began to focus on a computer program that would monitor physician’s prescriptions for antibiotics .

REQUIREMENTS☻access data bases on three Stanford

computers: clinical laboratory bacteriology systems and the pharmacy☻considerable knowledge about the general

and specific conditions that make one antibiotic, or combination of antibiotics.

Requirements continued….☻Before a system could monitor for inappropriate

therapeutic decisions, it would need to be an "expert" in the field of antimicrobial selection.

☻Thus, a monitoring system could be modified to

provide consultations to physicians.

☻Another appeal of focusing on an interactive system was that it provided us with a short-term means to avoid the difficulty of linking three computers together to provide data to a monitoring system.

☻Thus their concept of a computer-based consultant was born.

Whose EXPERTIES to be used? ☻Cohen interested Thomas Merigan, Chief of the

Infectious Disease Division at Stanford, in lending both his expertise

And that of ☻Stanton Axline, a physician in his division.☻Shortliffe synthesized medical knowledge from

Cohen and Axline

And☻AI ideas from Buchanan and Cordell Green.☻Axline subsequently enlisted help from

infectious disease fellows to complement.☻The expertise of" Cohen’s clinical

pharmacology fellows”.

MYCIN’s Task Domain Antimicrobial Selection

☻The sulfonamides in the 1930s and penicillin in 1943.

☻In the 1950s it became clear that antibiotics were being misused.

☻At the time they began work on MYCIN, antibiotic misuse was receiving wide attention .

☻The studies showed that very few physicians go through the methodical decision process.

☻In the outpatient environment antibiotics are often prescribed without the physician’s having identified or even cultured the offending organism.

Structure of MYCIN

Structure of MYCIN Continued….

Some main points about MYCIN☻ It is a rule based system.

☻MYCIN primarily uses backward chaining, or a goal-directed control strategy.

☻ It is built using LISP language.

☻CF’s are associated with all implications.

☻Meta-level reasoning is allowed in order to increase efficiency (e.g., using meta-rules or looking for a unity path).

☻MYCIN’s logic is incomplete in the sense that we know there are propositions that can be expressed in the language but are not provable as theorems.

A typical consultation

1) Patient’s name: (first-last) ** FRED BRAUN (Questions 1-3 request background patient

data.)2) Sex: **M3) Age: ** 554) Are there any cultures for Fred Braun 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 (System corrects typing error.)

Consultation continued…..

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-I) will be referred to as:

........ ORGANISM-1 ........

7) Enter the laboratory-reported identity of ORGANISM-l:**UNKNOWN (Typically identity is not yet

known.)•

Consultation continued……

8) The stain (gram or ZiehI-Neelsen acid-fast) of ORGANISM-l:

** 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.)?

** FUSlFORM

Consultation continued…..(... more questions follow in order to gather sufficient

information to infer the identity and significance of the infecting organisms... )

23) What is the suspected portal of entry of the gramneg rod from the blood culture of 20-JUN-77 (ORGANISM-I) into this sterile site?

** GI (6) (User indicates the uncertainty of his response.)

24) Is Fred Braun a burn patient? **N

Consultation continued…… 25) Is Fred Braun a compromised host(e.g.alcoholic,

sickle-cell disease,immunosuppressed)?

**N

26) Is Fred Braun febrile?

**y

(... after about 50-60 questions, MYClN prints the

diagnostic hypotheses on which therapy will be

based... )

How it works?

Positive culture

Suspected infection Previous treatment Current treatment

organism1

Gram positive

Known organism

Patient1

Culture1 Drug 6

Growth

A context tree for a patient

Stain

Start

Examine the first part in the condition

part of the rule

More tests?Is the test true?Get the information

needed withFINDOUT

Reject the rule

Examine the next test

Add the conclusion of the rule to the patient

context tree

Return

Can the test be evaluated?

No

YesYes

Yes

NoNo

The structure of MYCIN ‘s MONITOR

Return

The structure of MYCIN’s FINDOUT

Start

ReturnReturn

Is the item LABDATA?

Ask the user to carry out

the necessary test and enter

the result

Find the rules for chaining

with UPDATED BY

Apply MONITOR to the rules in turn

YesNo

Test which was conducted to evaluate the performance of MYCIN

Rule of checking….

Each judge was asked to score each

recommendation as

a) equivalent to their own best judgment,

b) not equivalent but acceptable, or

c) unacceptable.

Result of the test

Result Continued……☻What is the x axis of the graph?☻ It is unlabeled because the factors that

determine performance have not been explicitly identified.

☻What could these factors be? ☻Mycin certainly does mental arithmetic more

accurately and more quickly than Stanford faculty; perhaps this is why it performed so well.

☻Mycin remembers everything it is told; perhaps this explains its performance.

☻Mycin reasons correctly with conditional probabilities, and many doctors do not ;

perhaps this is why it did so well.

Any Question…?