On congruence modularity in varieties of logic.
The concept of a quasivariety of logic is introduced in the paper. It is shown that every congruence point regular quasivariety can serve as a quasivariety of logic. However, every congruence point regular variety is congruence modular, hence there is a natural question on congruence modularity of quasivarieties of logic. The authors answer this question in the negative. They construct an example of a quasivariety of logic which does not satisfy any non-trivial lattice identity for congruences.
scientific article; zbMATH DE number 1603138