On Free $\omega$-Continuous and Regular Ordered Algebras

We study varieties of certain ordered $\Sigma$-algebras with restricted completeness and continuity properties. We give a general characterization of their free algebras in terms of submonads of the monad of $\Sigma$-coterms. Varieties of this form are called \emph{quasi-regular}. For example, we sh...

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Main Authors: Zoltan Esik, Dexter Kozen
Format: Article
Language:English
Published: Logical Methods in Computer Science e.V. 2019-10-01
Series:Logical Methods in Computer Science
Subjects:
Online Access:https://lmcs.episciences.org/2586/pdf
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author Zoltan Esik
Dexter Kozen
author_facet Zoltan Esik
Dexter Kozen
author_sort Zoltan Esik
collection DOAJ
description We study varieties of certain ordered $\Sigma$-algebras with restricted completeness and continuity properties. We give a general characterization of their free algebras in terms of submonads of the monad of $\Sigma$-coterms. Varieties of this form are called \emph{quasi-regular}. For example, we show that if $E$ is a set of inequalities between finite $\Sigma$-terms, and if $\mathcal{V}_\omega$ and $\mathcal{V}_\mathrm{reg}$ denote the varieties of all $\omega$-continuous ordered $\Sigma$-algebras and regular ordered $\Sigma$-algebras satisfying $E$, respectively, then the free $\mathcal{V}_\mathrm{reg}$-algebra $F_\mathrm{reg}(X)$ on generators $X$ is the subalgebra of the corresponding free $\mathcal{V}_\omega$-algebra $F_\omega(X)$ determined by those elements of $F_\omega(X)$ denoted by the regular $\Sigma$-coterms. This is a special case of a more general construction that applies to any quasi-regular family. Examples include the *-continuous Kleene algebras, context-free languages, $\omega$-continuous semirings and $\omega$-continuous idempotent semirings, OI-macro languages, and iteration theories.
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spelling doaj.art-610a89e9ca654cc18009c2bd86c555e32024-03-08T10:29:38ZengLogical Methods in Computer Science e.V.Logical Methods in Computer Science1860-59742019-10-01Volume 15, Issue 410.23638/LMCS-15(4:4)20192586On Free $\omega$-Continuous and Regular Ordered AlgebrasZoltan EsikDexter KozenWe study varieties of certain ordered $\Sigma$-algebras with restricted completeness and continuity properties. We give a general characterization of their free algebras in terms of submonads of the monad of $\Sigma$-coterms. Varieties of this form are called \emph{quasi-regular}. For example, we show that if $E$ is a set of inequalities between finite $\Sigma$-terms, and if $\mathcal{V}_\omega$ and $\mathcal{V}_\mathrm{reg}$ denote the varieties of all $\omega$-continuous ordered $\Sigma$-algebras and regular ordered $\Sigma$-algebras satisfying $E$, respectively, then the free $\mathcal{V}_\mathrm{reg}$-algebra $F_\mathrm{reg}(X)$ on generators $X$ is the subalgebra of the corresponding free $\mathcal{V}_\omega$-algebra $F_\omega(X)$ determined by those elements of $F_\omega(X)$ denoted by the regular $\Sigma$-coterms. This is a special case of a more general construction that applies to any quasi-regular family. Examples include the *-continuous Kleene algebras, context-free languages, $\omega$-continuous semirings and $\omega$-continuous idempotent semirings, OI-macro languages, and iteration theories.https://lmcs.episciences.org/2586/pdfcomputer science - logic in computer science
spellingShingle Zoltan Esik
Dexter Kozen
On Free $\omega$-Continuous and Regular Ordered Algebras
Logical Methods in Computer Science
computer science - logic in computer science
title On Free $\omega$-Continuous and Regular Ordered Algebras
title_full On Free $\omega$-Continuous and Regular Ordered Algebras
title_fullStr On Free $\omega$-Continuous and Regular Ordered Algebras
title_full_unstemmed On Free $\omega$-Continuous and Regular Ordered Algebras
title_short On Free $\omega$-Continuous and Regular Ordered Algebras
title_sort on free omega continuous and regular ordered algebras
topic computer science - logic in computer science
url https://lmcs.episciences.org/2586/pdf
work_keys_str_mv AT zoltanesik onfreeomegacontinuousandregularorderedalgebras
AT dexterkozen onfreeomegacontinuousandregularorderedalgebras