Databases Reference
In-Depth Information
Turning the ignition switch on is one action in a complex of conditions
required to start the engine. One of the events might be used to represent
the collection of equal grain sized events; or, a higher level granule might
be specified with the understanding that it will invoke a set of finer-grained
events. In terms of nested granules, the largest grained view is: turning on the
switch is the sole causal element; the complex of other elements represents
the finer-grains. These elements in turn could be broken down into still finer-
grains; for example, “available fuel” could be broken down into:
fuel in tank, operating fuel pump, intact fuel lines, and so forth.
start car: turn on ignition switch
...
available
fuel
battery
operational
wires
connect:
battery to
ignition
switch
wires
connect:
ignition
switch to
starter,
spark
plugs
turn on
ignition
switch
fuel
in
tank
operating
fuel
pump
intact
fuel
lines
Fig. 1.
Nested causal complex
Sometimes, it is enough to know what happens at a large-grained level; at
other times it is necessary to know the fined grained result. For example, if
Bill believes that turning the ignition key of his automobile
causes
the
automobile to start.
It is enough if
Bill engages an automobile mechanic when his automobile does not
start when he turns the key on.
However,
The automobile mechanic needs to know a finer-grained view of an
automobile's causal complex than does Robin.
Instead of being concerned with all of the fined grained detail, a better
approach may be to incorporate granulation using rough sets and/or fuzzy
sets to soften the need for preciseness. And then accept impreciseness in the
description. Each complex can be considered to be a granule. Larger complexes
can be decomposed into smaller complexes. Thus, going from large-grained to
small-grained.
