In the framework of fuzzy algebras with fuzzy equalities and acomplete lattice as a structure of membership values, we investigate fuzzyequational classes. They consist of special fuzzy algebras fullling the samefuzzy identities, dened with respect to fuzzy equalities. We introduce basicnotions and the corresponding operators of universal algebra: construction offuzzy subalgebras, homomorphisms...

In our previous study, we were interested in the equational fragment of first-order fuzzy logic [2, 3]. It turned out that the models of the equational fragment (which we call algebras with fuzzy equalities) are interesting and natural structures by themselves. The present paper provides an introductory study to the structures of equational fragment of fuzzy logic. The paper is an excerpt from ...

We show that uniication in certain extensions of shallow equational theories is decidable. Our extensions generalize the known classes of shallow or standard equational theories. In order to prove de-cidability of uniication in the extensions, a class of Horn clause sets called sorted shallow equational theories is introduced. This class is a natural extension of tree automata with equality con...

The study of perfect, local and bipartite IMTL-algebras presented in [29] is generalized in this paper to the general non-involutive case, i. e. to MTL-algebras. To this end we describe the radical of MTL-algebras and characterize perfect MTL-algebras as those for which the quotient by the radical is isomorphic to the two-element Boolean algebra, and a special class of bipartite MTL-algebras, B...

Presented is a completeness theorem for fuzzy equational logic with truth values in a complete residuated lattice: Given a fuzzy set Σ of identities and an identity p ≈ q, the degree to which p ≈ q syntactically follows (is provable) from Σ equals the degree to which p ≈ q semantically follows from Σ. Pavelka style generalization of well-known Birkhoff’s theorem is therefore established.

We give a general method for constructing lattices L whose equational theories are inherently nonfinitely based. This means that the equational class (that is, the variety) generated by L is locally finite and that L belongs to no locally finite finitely axiomatizable equational class. We also provide an example of a lattice which fails to be inherently nonfinitely based but whose equational th...

We show that uni cation in certain extensions of shallow equational theories is decidable Our extensions generalize the known classes of shallow or standard equational theories In order to prove de cidability of uni cation in the extensions a class of Horn clause sets called sorted shallow equational theories is introduced This class is a natural extension of tree automata with equality constra...

We study direct limits and reduced products of algebras with fuzzy equalities. On the one hand, algebras with fuzzy equalities are natural fuzzy structures that disallow to map similar arguments to dissimilar ones. On the other hand, they are exactly the semantic structures of the equational fragment of first-order fuzzy logic. In this paper we propose generalizations of direct limits and reduc...