## BCK-meet-semilattices

Abbreviation: BCKJMlat

### Definition

A BCK-meet-semilattice is a structure $\mathbf{A}=\langle A,\wedge,\rightarrow,1\rangle$ of type $\langle 2,2,0\rangle$ such that

(1): $(x\rightarrow y)\rightarrow ((y\rightarrow z)\rightarrow (x\rightarrow z)) = 1$

(2): $1\rightarrow x = x$

(3): $x\rightarrow 1 = 1$

(4): $(x\wedge y)\rightarrow y = 1$

(5): $x\wedge((x\rightarrow y)\rightarrow y) = x$

$\wedge$ is idempotent: $x\wedge x = x$

$\wedge$ is commutative: $x\wedge y = y\wedge x$

$\wedge$ is associative: $(x\wedge y)\wedge z = x\wedge (y\wedge z)$

Remark: $x\le y \iff x\rightarrow y=1$ is a partial order, with $1$ as greatest element, and $\wedge$ is a meet in this partial order. 1)

##### Morphisms

Let $\mathbf{A}$ and $\mathbf{B}$ be BCK-meet-semilattices. A morphism from $\mathbf{A}$ to $\mathbf{B}$ is a function $h:A\rightarrow B$ that is a homomorphism:

$h(x\wedge y)=h(x)\wedge h(y)$, $h(x\rightarrow y)=h(x)\rightarrow h(y)$ and $h(1)=1$.

Example 1:

### Properties

Classtype variety yes yes yes, $n=2$

### Finite members

$\begin{array}{lr} f(1)= &1\\ f(2)= &\\ f(3)= &\\ f(4)= &\\ f(5)= &\\ f(6)= &\\ \end{array}$

### References

1) Pawel M. Idziak, Lattice operation in BCK-algebras, Math. Japon., 29, 1984, 839–846 MRreview