Fuzzy Querying Capability at Core of a RDBMS - Advanced Database Query Systems - page 165

Box 1.

Atomic Predicates with the syntax:
CREATE FUZZY PREDICATE <name> ON <dom> AS <fset>
where
<name> is a string of characters,

<dom> is the domain (possible values over the linguistic variable),

<fset> is the specification of a Fuzzy Set with one of the follow-

ing forms:
A trapezoidal function with four parameters
(<support 1 >, <core 1 >, <core 2 >, <support 2 >)
A Fuzzy Set for extension, i.e.
{<value 1 >/<µ 1 >,...,<value n >/< µ n >}
An arithmetic expression with the variable <x> that indicates the
predicate´s argument.
Fuzzy modifiers with the syntax:
CREATE MODIFIER <name> AS POWER <n>
or
CREATE MODIFIER <name> AS <exp> POWER <n>
or
CREATE MODIFIER <name> AS TRANSLATION <d>
where
<name> is a string of characters,
<n> is a power to the membership degree,
<exp> is an arithmetic expression with the variables <x> and <y>
indicating the first and second term respectively
<d> is a value for translation of the original predicate
Fuzzy comparison with the syntax:
CREATE COMPARATOR <name> ON <dom> AS <exp>
where
<name> is a string of characters
<dom> is the domain (possible values over the linguistic variable)
<exp> is an expression to calculate the value of the comparator
through two elements. It may be a Fuzzy Set like:
A trapezoidal function with four parameters (<exp 1 >, <exp 2 >, <exp 3 >,
<exp 4 >) that are arithmetic expressions with the variables <x> and <y> indicat-
ing the first and second term respectively,
{<(value 11 ,value 12 )>/<µ 1 >,..., <(value nn , value nm )>/<µ n >} and value ij (i
between 1 and n, j between 1 and m) are pairs of values in the domain with re-
spective membership degrees.
Fuzzy connectors with the syntax:
CREATE CONNECTOR <name> AS <exp>
where
<name> is a string of characters