Kleene posets and pseudo-Kleene posets

TL;DR

This paper extends the theory of Kleene and pseudo-Kleene structures from lattices to posets, characterizes them via identities, and explores their completions and embeddings, revealing new algebraic and order-theoretic properties.

Contribution

It introduces the concepts of (pseudo-)Kleene posets, characterizes them with identities, and shows how they relate to Kleene algebras through completions and embeddings.

Findings

Dedekind-MacNeille completion of pseudo-Kleene posets yields pseudo-Kleene algebras

Finite Kleene posets' completions are Kleene algebras

Every poset can be embedded into a pseudo-Kleene poset

Abstract

The concept of a Kleene algebra (sometimes also called Kleene lattice) was already generalized by the first author for non-distributive lattices under the name pseudo-Kleene algebra. We extend these concepts to posets and show how (pseudo-)Kleene posets can be characterized by identities and implications of assigned commutative meet-directoids. Moreover, we prove that the Dedekind-MacNeille completion of a pseudo-Kleene poset is a pseudo-Kleene algebra and that the Dedekind-MacNeille completion of a finite Kleene poset is a Kleene algebra. Further, we introduce the concept of a strict (pseudo-)Kleene poset and show that under an additional assumption a strict Kleene poset can be organized into a residuated structure. Finally, we prove by using the so-called twist construction that every poset can be embedded into a pseudo-Kleene poset in some natural way.