Аннотации:
We show that for every quasivariety K of structures (where
both functions and relations are allowed) there is a semilattice S with
operators such that the lattice of quasi-equational theories of K (the dual
of the lattice of sub-quasivarieties of K) is isomorphic to Con(S;+; 0; F).
As a consequence, new restrictions on the natural quasi-interior operator
on lattices of quasi-equational theories are found.