---
title: "Formalizing and Using Persistency"
authors:
  - "Thomas Guckenbiehl"
doi: ""
url: "https://ijcai.org/proceedings/1991/16"
pdf: "https://ijcai.org/proceedings/1991/0016.pdf"
venue: "Proceedings of the Twelfth International Joint Conference on Artificial Intelligence"
year: 1991
pages: "105-109"
track: "Automated Reasoning"
keywords:
---

# Formalizing and Using Persistency

Thomas Guckenbiehl

*Proceedings of the Twelfth International Joint Conference on Artificial Intelligence*, pages 105-109.

## Abstract

In many formalizations of a changing world things do not change all the time but are persistent thoughout a time interval. Often this persistency is represented by facts refering to intervals int which are still valid if int is replaced by any subinterval int'. Approaches like episode propagation or Penberthy's temporal unification try to employ this property for efficient reasoning. However these approa~hes lack formality. In this paper their way of reasonmg about persistency is reconstructed as inference rules that combine appropriate timeboxes with standard resolution. In many cases BOrckert's Constrained Resolution may be used. ~ore complex examples may be handled by a new mference rule, called Persistency Resolution. An analysis of this rule leads to a more general notion of persistency.