---
title: "Definability of Horn Revision from Horn Contraction"
authors:
  - "Zhi Qiang Zhuang"
  - "Maurice Pagnucco"
  - "Yan Zhang"
doi: ""
url: "https://ijcai.org/proceedings/2013/181"
pdf: "https://ijcai.org/proceedings/2013/0181.pdf"
venue: "Proceedings of the Twenty-Third International Joint Conference on Artificial Intelligence"
year: 2013
pages: "1205-1211"
track: ""
keywords:
---

# Definability of Horn Revision from Horn Contraction

Zhi Qiang Zhuang, Maurice Pagnucco, Yan Zhang

*Proceedings of the Twenty-Third International Joint Conference on Artificial Intelligence*, pages 1205-1211.

## Abstract

In the AGM framework [Alchourron and Makinson, 1985], a revision function can be defined directly through constructions like systems of spheres, epistemic entrenchment, etc., or indirectly through a contraction operation via the Levi identity. A recent trend is to construct AGM style contraction and revision functions that operate under Horn logic. A direct construction of Horn revision is given in [Delgrande and Peppas, 2011]. However, it is unknown whether Horn revision can be defined indirectly from Horn contraction. In this paper, we address this problem by obtaining a model-based Horn revision through the model-based Horn contraction studied in [Zhuang and Pagnucco, 2012]. Our result shows that, under proper restrictions, Horn revision is definable through Horn contraction via the Levi identity.