ABSTRACT
Furthermore, it was pointed out that many systems make use of the closed-
world assumption, whereby any hypothesis that is unknown is assumed to be
false. We were then left with a binary system, where everything is either true
or false. While this model of reality is useful in many applications, real
reasoning processes are rarely so clear-cut. Referring to the example of the
control of a power station boiler, we made use of the following rule:
IF transducer output is low THEN water level is low
There are three distinct forms of uncertainty that might be associated with this
rule:
Uncertainty in the rule itself
A low level of water in the drum is not the only possible explanation for a low
transducer output. Another possible cause could be that the float attached to
the transducer is stuck. What we really mean by this rule is that if the
transducer output is low then the water level is probably low.
