In combination with a d-parameter the preference order of numerical base preferences can further be manipulated. In the most basic case, numerical base preferences as sub-constructors of SCOREd evaluate attribute values of tuples by using a scoring function f(x). With a d-paramater applied, level values are generated by fd(x) with level 0 containing the most preferred elements. The c-parameter now defines a starting level c from which on all elements are considered as equally preferrable. If we define the level l(x) of an element x as:
then the c-parameter implements the following rule:
<Numerical_Base_Preference>, [<d>] [, <c>]
For the use case of purchasing a new car, consumers may decide that intervals of 100 EUR are precise enough to describe their preference with respect to the price. Deviations of more than 500 EUR are equally bad. The price should be between 2000 EUR and 5000 EUR.
PREFERRING price BETWEEN 2000 AND 5000, 100, 5
PREFERRING price AROUND 10000, 100, 5
PREFERRING price LOWEST 0, 100, 5