---
title: "Extending a Knowledge-Based System to Deal with Ad Hoc Constraints"
authors:
  - "John P. McDermott"
  - "Barbara Steele"
doi: ""
url: "https://ijcai.org/proceedings/1981/157"
pdf: "https://ijcai.org/proceedings/1981/0157.pdf"
venue: "Proceedings of the Seventh International Joint Conference on Artificial Intelligence"
year: 1981
pages: "824-827"
track: "Expert Systems"
keywords:
---

# Extending a Knowledge-Based System to Deal with Ad Hoc Constraints

John P. McDermott, Barbara Steele

*Proceedings of the Seventh International Joint Conference on Artificial Intelligence*, pages 824-827.

## Abstract

R1 is a rule based program used by Digital Equipment Corporation 's monufac.turing organization for configuring VAX - 11 systems. Since its inception . R1 has had the capability of producing a functional system by fleshing out an order consisting only of a CPU, ·some primary memory, and some devices; until recently , however, it was not capable of accepting as part of its input a set of ad hoc (customer-specific) constraints. Left to itself, R1 was capable of producing reasonable configurations. But it was incapable of modifying its decisions on the basis of information that others could provide. This paper describes how rules were added to R1 to take advantage of such information . R1 can now accept as input commands that specify how particular components are to be configured. Whenever one of the commands becomes relevant, these rules take control, t'xtend the configuration in the direction indicated by the command, and then step aside, allowing R1 's ordinary-case configuration rules to regain control.