## Boolean algebras with operators

Abbreviation: BAO

### Definition

A Boolean algebra with operators is a structure $\mathbf{A}=\langle A,\vee,0, \wedge,1,\neg,f_i\ (i\in I)\rangle$ such that

$\langle A,\vee,0,\wedge,1,\neg\rangle$ is a Boolean algebra

$f_i$ is join-preserving in each argument: $f_i(\ldots,x\vee y,\ldots)=f_i(\ldots,x,\ldots)\vee f_i(\ldots,y,\ldots)$

$f_i$ is normal in each argument: $f_i(\ldots,0,\ldots)=0$

##### Morphisms

Let $\mathbf{A}$ and $\mathbf{B}$ be Boolean algebras with operators of the same signature. A morphism from $\mathbf{A}$ to $\mathbf{B}$ is a function $h:A\rightarrow B$ that is a Boolean homomorphism and preserves all the operators:

$h(f_i(x_0,\ldots,x_{n-1}))=f_i(h(x_0),\ldots,h(x_{n-1}))$

Example 1:

### Properties

Classtype variety decidable undecidable no unbounded yes yes yes, $n=2$ yes yes yes no no yes yes yes