---
title: "Plan Modification versus Plan Generation: A Complexity-Theoretic Perspective"
authors:
  - "Bernhard Nebel"
  - "Jana Koehler"
doi: ""
url: "https://ijcai.org/proceedings/1993/199"
pdf: "https://ijcai.org/proceedings/1993/0199.pdf"
venue: "Proceedings of the Thirteenth International Joint Conference on Artificial Intelligence"
year: 1993
pages: "1436-1443"
track: "Planning"
keywords:
---

# Plan Modification versus Plan Generation: A Complexity-Theoretic Perspective

Bernhard Nebel, Jana Koehler

*Proceedings of the Thirteenth International Joint Conference on Artificial Intelligence*, pages 1436-1443.

## Abstract

The ability of a planner to modify a plan is considered as a valuable tool for improving efficiency of planning by avoiding the repetition of the same planning effort. From a computational complexity point of view, however, it is by no means obvious that modifying a plan is computationally as easy as planning from scratch if the modification has to follow the principle of "conservatism," i.e., to reuse as much of the old plan as possible. Indeed, considering propositional STRIPS planning, it turns out that conservative plan modification is as hard as planning and can sometimes be harder than plan generation. Furthermore, this holds even if we consider modification problems where the old and the new goal specification are similar. We put these results into perspective and discuss the relationship to existing plan modification systems.