Case Study 2- 1
Consider the following five production rules:
56:166 Production Systems
R1:
R2:
Case Study 2
R3:
R4:
R5:
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IF temperature is high
THEN pressure is high
IF pressure is high
AND fluid level is high
THEN status is dangerous
IF indicator is on
THEN temperature is high
IF status is dangerous
THEN relay is on
IF relay is on
AND standby unit is off
THEN indicator is on
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Solution
Perform
R1:
a) Draw an AND/OR inference tree
R2:
b) List anomalies, if any
R3:
c) Indicate a possible source of inconsistency and modify
R4:
appropriate production rule(s) to eliminate the anomaly
R5:
E
R5
IF temperature is high (A)
THEN pressure is high (B)
IF pressure is high (B)
AND fluid level is high (C)
THEN status is dangerous (D)
IF indicator is on (E)
THEN temperature is high (A)
IF status is dangerous (D)
THEN relay is on (F)
IF relay is on (F)
AND standby unit is off (G)
THEN indicator is on (E)
G
F
R4
R3
D
R2
B
C
R1
A
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To eliminate the cycle R3 - R1 - R2 - R4 - R5,
rules R3 and R5 are modified as follows:
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A: temperature is high
E
Solution H
R5
R5
B: pressure is high
G
F
C: fluid level is high
R3: IF indicator is on
R3: IF indicator 1 is on
THEN temperature is high
THEN temperature is high
R5: IF relay is on
AND standby unit is off
THEN indicator is on
D: status is dangerous
R5: IF relay is on
AND standby unit is off
THEN indicator 2 is on
R3
E: indicator 1 is on
G: standby unit is off
H: indicator 2 is on
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R4
D
D
R2
B
F: relay is on
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R4
R2
B
Old
G
F
C
R1
A
A
R3
Old
C
R1
E
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R1 : IF tool = available AND fixture = available
Case Study 2-2
F
G
C
THEN auxiliary devices = available
R4
D
R2 : IF auxiliary devices = available AND machine = available
An expert in machine tool products has generated
a few production rules.
D
E
THEN resources = available
A
B
R2
R3
A
H
R3 : IF buffer = not empty
a) Draw an AND/OR tree
b) List the sequence of firing the rules using
the forward-chaining inference strategy
H
THEN part = available
D
B
R1
R4 : IF resources = available AND part = available
A
E
B
THEN machine status = machining
C
F
G
Sequence of Firing Rules R1 -- R2 -- R3 -- R4
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