Abbreviation: BLA
A \emph{basic logic algebra} or \emph{BL-algebra} is a structure $\mathbf{A}=\langle A,\vee ,0,\wedge ,1,\cdot ,\to \rangle $ such that
$\langle A,\vee ,0,\wedge ,1\rangle $ is a bounded lattice
$\langle A,\cdot ,1\rangle $ is a commutative monoid
$\to$ gives the residual of $\cdot $: $x\cdot y\leq z\Longleftrightarrow y\leq x\to z$
prelinearity: $( x\to y) \vee ( y\to x) =1$
BL: $x\cdot(x\to y)=x\wedge y$
Remark: The BL identity implies that the lattice is distributive.
A \emph{basic logic algebra} is a FLe-algebra $\mathbf{A}=\langle A,\vee ,0,\wedge ,1,\cdot ,\to \rangle $ such that
linearity: $( x\to y) \vee ( y\to x) =1$
BL: $x\cdot (x\to y)=x\wedge y$
Remark: The BL identity implies that the identity element $1$ is the top of the lattice.
Let $\mathbf{A}$ and $\mathbf{B}$ be basic logic algebras. A morphism from $\mathbf{A}$ to $\mathbf{B}$ is a function $h:A\to B$ that is a homomorphism:
$h(x\vee y)=h(x)\vee h(y)$, $h(1)=1$, $h(x\wedge y)=h(x)\wedge h(y)$, $h(0)=0$, $h(x\cdot y)=h(x)\cdot h(y)$, $h(x\to y)=h(x)\to h(y)$
Example 1:
$\begin{array}{lr}
f(1)= &1
f(2)= &1
f(3)= &2
f(4)= &5
f(5)= &10
f(6)= &23
f(7)= &49
f(8)= &111
\end{array}$
The number of subdirectly irreducible BL-algebras of size $n$ is $2^{n-2}$.