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Kuipers(Kuipers,1984). Physical systems involved in De Kleer's qualitative
model approach are composed of devices such as the tubes, valves and containers,
etc. Constraint conditions (qualitative equations) reflect at the junctions of these
devices, giving qualitative explanation according to qualitative equations. In
Forbus's qualitative process approach, the change of a physical system is caused
by processes and a physical course is described by some processes. Kuipers
directly uses the parameters of the part as the state variables to describe the
physical structure. Qualitative restraint is generated by the physical law directly.
One parameter's changing with time is regarded as the qualitative state array.
Solution algorithm proceeds from initial state, produces the follow-up states of
different possibility, and then repeats this course through the filtration of
consistency until no new state to appear.
Besides above three kinds of basic approaches, there are other research works.
Davis has proposed a fault diagnosis approach from the structure description.
Reiler has proposed a fault diagnosis approach from basic principle. Williams has
built a mixed algebra system Q1, which combines qualitative operation and
qualitative reasoning, and has discussed algebra property of it. He has also
realized designing qualitative reasoning with qualitative equation. Iwasaki and
Simmons have applied causality formalized characteristic and comparatively
static approach used in economics and thermodynamics to qualitative causality
analysis, and have given a formalized definition to causality. Weld has designed
the qualitative simulation program in molecular biology, has found out the
circulation appearing repeatedly with cluster approach, and has also discussed the
situation of non-continuous quantity through confirming the last state of the
system by the analysis of circulation.
4.2 Basic approaches in qualitative reasoning
Human's description or explanation towards physical world usually proceeds
with certain intuitive qualitative way. Differential equation and concrete number
value are seldom involved. For example, to avoid people's falling down or
colliding when riding a bicycle, the motion equations are not necessary. Only
intuitive but roughly accurate description according to the changing trend of
several main parameters is enough.
Generally, the standard course to analyze the behaviors in motion system can
be divided into three steps:
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