Multi-argument specialization semilattices

TL;DR

This paper introduces axioms for multi-argument specialization semilattices derived from closure spaces, providing completeness and embedding results that connect these algebraic structures with closure space models.

Contribution

It formulates a complete axiom system for multi-argument specialization semilattices and establishes their embedding into closure space-based structures.

Findings

Axioms characterize multi-argument specialization semilattices.

Every model satisfying the axioms embeds into a closure space structure.

Canonical embedding into closure semilattices is constructed.

Abstract

If $X$ is a closure space with closure $K$, we consider the semilattice $(\mathcal P(X), \cup)$ endowed with further relations $ x \sqsubseteq y_1, y_2, \dots, y_n$ (a distinct $n+1$-ary relation for each $n \geq 1$), whose interpretation is $x \subseteq Ky_1 \cup Ky_2 \cup \dots \cup Ky_n $. We present axioms for such "multi-argument specialization semilattices" and show that this list of axioms is complete for substructures, namely, every model satisfying the axioms can be embedded into some structure originated by some closure space as in the previous sentence. We also provide a canonical embedding of a multi-argument specialization semilattice into (the reduct of) some closure semilattice.