---
title: "Subgoal Protection and Unraveling During Plan Synthesis"
authors:
  - "Chuck Rieger"
  - "Philip London"
doi: ""
url: "https://ijcai.org/proceedings/1977/109"
pdf: "https://ijcai.org/proceedings/1977/0109.pdf"
venue: "Proceedings of the Fifth International Joint Conference on Artificial Intelligence"
year: 1977
pages: "487-492"
track: "Problem-solving and Search"
keywords:
---

# Subgoal Protection and Unraveling During Plan Synthesis

Chuck Rieger, Philip London

*Proceedings of the Fifth International Joint Conference on Artificial Intelligence*, pages 487-492.

## Abstract

Subgoal annihilation occurs during plan syntnes~s when the solution of a later subgoal undoes or interferes with a completed solution to a preceding subgoal. Subgoal annihilation during plan synthesis is discussed, and a uniforrJ solution to the general problem is presented. The two phases of the theory are detection and correction of annihilation errors. Detection is carried out via a theory of spontaneous computation in which so-called "guardian clusters" watch over synthesized goals. Correction is accomplished by a give and take technique called "unravelling," wherein conflicting parts of the plan back off temporarili to allow other parts to co1aplete. The theoretica framework of the plan synthesizer is described, a detailed computer example of detection and unravelling is given, and other applications motivated by this theory are suggested.