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Introduction to Expert Systems: MYCIN1
MYCIN was the first large expert system to perform at the level of a human expert and to
provide users with an explanation of its reasoning
...
Moreover, the
techniques developed for MYCIN have become widely available in the various small
expert system building tools
...
It was designed
to aid physicians in the diagnosis and treatment of meningitis and bacteremia infections
...
AI investigators wanted to advance the state of
expert system building by undertaking a hard problem with clear, practical ramifications
...
These infectious diseases can be fatal and often show
themselves during hospitalization
...
The need to act quickly further
compounds the problem
...
In many cases, the physician must begin treatment in the absence of complete
lab results
...

MYCIN is a computer program designed to provide attending physicians with
advice comparable to that which they would otherwise get from a consulting physician
specializing in bacteremia and meningitis infections
...
When the MYCIN program is evoked, it initiates a dialogue
...
Eventually MYCIN provides a diagnosis and a
detailed drug therapy recommendation
...
It considers, for example,
laboratory results of body fluid analyses, symptoms that the patient is displaying, and
general characteristics of the patient, such as age and sex
...
A MYCIN consultation proceeds in two
phases
...
Then
one or more drugs are prescribed that should control for all of the possible organisms
...
and D
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Artificial Intelligence in Business
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The antibiotics prescribed must rid the patient of the disease
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MYCIN may ask for the results of a test that has not yet been completed
...
This is proper because, when diagnosing
infections, doctors rarely have the luxury of perusing a complete set of laboratory data
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MYCIN accommodates to this situation by accepting UNKNOWN as a
response
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In addition to unknown information, there also may be information of which the
doctor is uncertain
...
To accommodate uncertainty, all information given to MYCIN may be
qualified by a certainty factor- a number between - 1 and + 1- that indicates the doctor's
degree of confidence in the answer to a question
...
4" to indicate a limited confidence in the response
...
MYCIN is able to respond to
such queries and, within constraints, can explain its reasoning
...
After diagnosis and prescription are complete, the physician
can if desired, trace MYCIN's entire diagnostic trail
...
The dialogue between MYCIN and the physician is below, with the
physician's responses underlined
...

************************************************************************
MYCIN begins by asking for four pieces of information about the patient name, age, sex,
and race
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1) Please enter information about the patient
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2) Are there any positive cultures obtained from SALLY? No
2

3) Are there any pending cultures of SALLY? Yes
4) Site: CSF
Date collected: 3-jun –75
Stain examined? Yes
Method of Collection: (urine, sputum only) N/A
5) Stain of smear: Morph: (type NONE if no organism was seen on the smear) None
The second piece of information that MYCIN wants concerns the availability of cultures
with positive readings
...
In this case the how the physician does not
have any positive cultures, and so MYCIN probes further (question 3), asking whether
this patient has pending cultures
...
MYCIN is unable to reach conclusions
from laboratory findings, but like the physician, MYCIN continues to ask questions
...
)? Yes
14) Has SALLY recently had objective evidence of abnormal neurologic signs (nuchal
rigidity, coma, seizures, etc
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MYCIN's questions 13 and 14 show a more traditional approach to the diagnosis by
symptoms, and after receiving the answer to question 14, MYCIN reports its first
conclusion: The CSF Infection is likely to be meningitis
...
Further questions lead to the following:
34) Is the meningitis a hospital-acquired infection? No
35) Is SALLY's clinical history consistent with EPIGLOTTITIS? No
36) Is SALLY's clinical history consistent with OTITIS-MEDIA? No
37) Has the patient ever been to an area that is endemic for coccidiomycoses?
Unknown
38) Is SALLY a burn patient? Why

3

When asked whether the patient is a burn victim (question 38), the physician responds by
typing WHY MYCIN responds by restating its understanding of "why" in this context, and
then explains what the information will be used for
...

[i
...
WHY is it important to determine whether SALLY has been seriously burned?]
[4
...

It has already been established that
[4
...
2] organisms were not seen on the stain of the pending csf culture (CULTURE- 1), and
[4
...
4] SALLY has been seriously burned
then
there is suggestive evidence that Pseudomonas-aeruginosa is one of the organisms (other
than those seen on cultures or smears) which might be causing the infection [RULE578]
[back to question 38
...
3
The physician is curious about how MYCIN was able to conclude that the type of
infection is bacterial
...
3" is a request to explain how MYCIN established clause
[4
...
MYCIN responds with its understanding of the
question, and then reports the rules it used in determining this fact
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5 to track down what heuristic Rule 500 is and
how it was confirmed
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Notice that MYCIN has four rules that support the likelihood that the infection is
bacterial, and one rule that suggests (certainty factor of
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MYCIN is considering both possibilities
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[i
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HOW was it established that the type of the infection may be bacterial?]
The following rules concluded about: the likelihood that the type of the infection may be
bacterial

Rule
[4
...
6] RULE501

Yes
(
...
17)
4

[4
...
8] RULE524
[4
...
1)
(
...
28)

Thus, it has been established that the type of the infection may be bacterial
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MYCIN checks for known allergies (question 43), for other characteristics
that relate to the use of particular medications, and then for the patient's weight
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It is important to cover for the following probable infection(s) and
associated organism(s):
INFECTION-1 is MENINGITIS
+ MYCOBACTERIUM-TB [from clinical evidence only]
+
...

CRYPTOCOCCUS [from clinical evidence only]
43) Does SALLY have a clinically significant allergic reaction to any antimicrobial
agent? No
[Considering ETHAMBUTAL-AND-INH-AND-RIFAMPIN for use against
INFECTION-1
...
3
From these 46 questions MYCIN makes a prescription (REC- I ), explains its reasoning,
and proposes additional tests and procedures
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289 (13
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5 100mg-tablets) q24h PO [calculated on basis of 15 mg/kg]
[The dose should be modified in renal failure
...
]
5

Comments: Periodic vision screening tests are recommended for optic neuritis
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0 100mg-tablets) q24h PO [calculated on basis of 10 mg/kg]
3) RIFAMPIN
Dose: 600 mg PO q24h
Comments: Administer dose on an empty stomach
...
Please obtain samples for
fungal, TB, and viral cultures, cytology, VDRL (blood and CSF), cryptococcal antigen
(blood and CSF), viral titers (blood and CSF)
...

************************************************************************
MYCIN's explanations, although quite useful, are limited to a review of its
reasoning process and a display of its knowledge
...
That is, the physician cannot ask
WHY RULE578 or WHAT IS PSEUDOMONAS AERUGINOSA
...

It is assumed that the terms MYCIN uses and the answers it requests are familiar
to the physicians using the program
...
The knowledge engineers
who built MYCIN were responsible for making sure that terms such as "culture,"
"staining," and "Mycobacterium-TB" would be familiar terms to MYCIN's users
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Its success with several hundred
cases has confirmed its competence in identifying the infectious agents, selecting
appropriate doses of effective drugs, and recommending additional diagnostic tests
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The task used
for this test was the selection of drugs for cases of infectious meningitis before the
causitive agent had been identified
...
In the second phase, prominent infectious disease specialists assessed each set
of cases and reviewed the diagnoses and prescriptions without knowing either the identity
of the prescribers or that one was a computer
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MYCIN and three of the faculty prescribers consistently
prescribed therapy that would have been effective in all 10 cases
...
Using this criterion, MYCIN received a
higher rating than N any of the human prescribers
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5 to 62
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MYCIN's strength in this test against highly qualified human physicians is based
on at least four factors:
♦ MYCIN's knowledge base, derived from some of the best human practitioners, is
extremely disease detailed and is as comprehensive as that of most physicians in
the domain of meningitis
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It considers every
possibility
...
" MYCIN considers every possible
disease it knows about
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No matter how obvious the disease is, MYCIN method of medically
checks for all of the details and considers all alternatives
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Several of its therapy recommendations are based on recent data
published in specialized journals
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The various evaluations that have been undertaken all suggest that MYCIN is as good or
better than most very skilled human experts
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Unlike traditional computer programs, which are very difficult to
modify, MYCIN is easy to change
...
Any
particular rule can be removed and the system will still run
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Rules can be changed in minutes using English-like input
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The ability to add rules and modify reasoning is a key characteristic of expert
systems
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Expert systems are developed and maintained
incrementally with the active involvement of one or more experts
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7

SUMMARY
MYCIN represents the first of a new generation of computer programs that reason
about the world, explain their reasoning, and provide advice that is comparable to advice
provided by human experts
...

MYCIN's success proved that expert systems technology was strong enough to leave the
laboratory, with its academic and well-circumscribed problems, and enter commercial
environments with their incomplete and uncertain information, skeptical users who
demand justifications, and domains where substantial amounts of knowledge are the
prerequisite of good judgment

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Title: Artificial intelligence Expert System- Mycin
Description: In this you ll get the brief and easy to understand.

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