Boolean algebras with operators
A Boolean algebra with operators is a structure A = (A,∨,0, ∧,1,¬,fi (i ∈ I)) such that
(A,∨,0,∧,1,¬) is a Boolean algebra,
fi is join-preserving in each argument:
fi( . . .,x∨y, . . .) = fi( . . .,x, . . .)∨fi( . . .,y, . . .), and
fi is normal in each argument: fi( . . .,0, . . .) = 0 for each i ∈ I.
Let A and B be Boolean algebras with operators of the same signature. A morphism from A to B is a function h : A→B that is a Boolean homomorphism and preserves all the operators: h(fi(x0, . . .,xn−1)) = fi(h(x0), . . .,h(xn−1)).
| Classtype | variety |
| Equational theory | decidable |
| Quasiequational theory | |
| First-order theory | undecidable |
| Locally finite | no |
| Residual size | unbounded |
| Congruence distributive | yes |
| Congruence modular | yes |
| Congruence n-permutable | yes, n = 2 |
| Congruence regular | yes |
| Congruence uniform | yes |
| Congruence extension property | yes |
| Definable principal congruences | no |
| Equationally definable principal congruences | no |
| Amalgamation property | yes |
| Strong amalgamation property | yes |
| Epimorphisms are surjective | yes |