Databases Reference
In-Depth Information
1.5% interest rate to an
Asian
group of closed account customers, the offer
may entice these customers to re-open their accounts. Sending that offer by
regular mail or giving a call to all these customers are examples of an action
associated with that E-action rule.
3 Information System and Action Rules
An information system is used for representing knowledge. Its definition, pre-
sented here, is due to Pawlak [7].
By an information system we mean a pair
S
=(
U,A
), where:
•
U
is a nonempty, finite set of objects
•
A
is a nonempty, finite set of attributes i.e.
a
:
U
−→
V
a
is a function for
any
a
∈
A
,where
V
a
is called the domain of
a
Elements of
U
are called objects. In this chapter, for the purpose of clarity,
objects are interpreted as customers. Attributes are interpreted as features
such as, offers made by a bank, characteristic conditions etc.
We consider a special case of information systems called decision tables
[7-9]. In any decision table together with the set of attributes a partition
of that set into conditions and decisions is given. Additionally, we assume
that the set of conditions is partitioned into stable conditions and flexible
conditions. For simplicity reason, we assume that there is only one decision
attribute.
Date of birth
is an example of a stable attribute. The
interest rate
on any customer account is an example of a flexible attribute as the bank can
adjust rates. We adopt the following definition of a decision table:
By a decision table we mean any information system
S
=(
U,A
St
∪
A
Fl
∪
{
A
Fl
is a distinguished attribute called the decision. The
elements of
A
St
are called stable conditions, whereas the elements of
A
Fl
are
called flexible conditions.
As an example of a decision table we take
S
=(
d
}
), where
d
∈
A
St
∪
{
x
1
,x
2
,x
3
,x
4
,x
5
,x
6
,x
7
,x
8
}
,
{
a,c
}∪{
b
}∪{
d
}
) represented by Table 1. The set
{
a,c
}
lists stable attributes,
Tabl e 1 .
Decision system
abcd
x
1
0
S
0
L
x
2
0
R
1
L
x
3
0
S
0
L
x
4
0
R
1
L
x
5
2
P
2
L
x
6
2
P
2
L
x
7
2
S
2
H
x
8
2
S
2
H
