Abstract
A fuzzy (linguistic) truth value is
a truth value specified by a fuzzy set over a closed interval $[0,1]$.
Logical operations, defined according to the extension
principle, do not satisfy all identities to be lattice
because there are subnormal truth values and non-convex truth values
that violate the absorption laws.
In 2000, Brzozowski proposed de Morgan bisemilattice, which is
generalized algebra of de Morgan lattice in order for applications in
multi-valued simulations of digital circuits.
This paper studies a notion of fuzzy-interval equivalnt relation
defined for fuzzy functions taking linguistic truth value.
