Abstract. Some elements of tame congruence theory can be applied to quasiorder lattices instead of congruence lattices. In particular, it is possible to consider minimal sets of an algebra with respect to one of its prime quasiorder quotients. It turns out that if a finite algebra is in a congruence modular variety, then it is minimal with respect to a quasiorder quotient iff it is minimal with respect to a congruence quotient --- in which case it is either a two-element algebra, or has a Mal'tsev-polynomial. As an application of this fact, we prove that if an algebra is in a congruence modular variety, its congruence and quasiorder lattices satisfy the same identities.

DOI: 10.14232/actasm-018-024-4

AMS Subject Classification (1991): 08A30, 08B10, 06B15

Keyword(s): quasiorder, modularity, lattice identity

received 22.2.2018, revised 27.1.2020, revised 9.3.2020, accepted 11.3.2020. (Registered under 24/2018.)