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A function T : [0, 1] × [0, 1] → [0, 1] is called an Archimedean t -norm iff there
exists a decreasing and continuous function f : [0, 1] → [0, ∞] with f (1) = 0:
1
Txyf fx fy
(,)
=
( () ())
+
(3.1)
3.3.2 t -Conorm
A t -conorm T * : [0, 1] → [0, 1] is a kind of binary operation used in the frame-
work of fuzzy logic and probabilistic metric spaces. It represents union in
fuzzy set theory or an 'ORing' operator. The four basic t -conorms are
* (,)max(,)
1. Zadeh's union: Txy
=
x y
M
* (,) =+−⋅
2. Product union: Txyxyxy
P
* (,)min(
3. Lukasiewicz union: Txy
=
x
+
y
, )
1
L
* (,) max( , ,
,
4. Nilpotent T -conorm: Txy
=
xy xy
if
otherwise
+<
1
n
0
Definition: : T * : [0, 1] × [0, 1] → [0, 1] is a t -conorm iff it satisfies the following
properties where x , y , z ∈ [0, 1] [12,15]:
1. Boundary condition: T * (0, 0) = 0 and T * (0, 1) = T * (1, 0) = T * (1, 1) = 1.
2. Commutativity: T * ( x , y ) = T * ( y , x ).
3. Monotonicity: T * ( x , y ) ≤ T * ( x , z ) if y z .
4. Associativity: T * ( T * ( x , y ), z ) = T * ( x , T * ( y , z )).
5. Zero identity: T * ( x , 0) = x .
6. A T -conorm, T *, is called Archimedean iff.
7. T * is continuous.
8. T * ( x , x ) > x for all x ∈ (0, 1).
A function T * : [0, 1] × [0, 1] → [0, 1] is called an Archimedean t -conorm iff
there exists an increasing and continuous function g : [0, 1] → [0, ∞] with
g (0) = 0:
* (,)
1
Txyggx gy
=
( () ())
+
(3.2)
f and g are additive generators.
There are many triangular operators, and they are classified as a class of
(1) conditional operators and (2) algebraic operators [7,12,15,18]. Conditional
operators contain min or max operators or the combination of min and
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