---
title: "A Logic for Representing Default and Prototypical Properties"
authors:
  - "James P. Delgrande"
doi: ""
url: "https://ijcai.org/proceedings/1987/84"
pdf: "https://ijcai.org/proceedings/1987/0084.pdf"
venue: "Proceedings of the Tenth International Joint Conference on Artificial Intelligence"
year: 1987
pages: "423-428"
track: "Knowledge Representation"
keywords:
---

# A Logic for Representing Default and Prototypical Properties

James P. Delgrande

*Proceedings of the Tenth International Joint Conference on Artificial Intelligence*, pages 423-428.

## Abstract

The area of default reasoning may be considered as consisting of two separate but closely related subareas . The first deals with representing default information . and addresses issues such as reasoning about default statements or determining the consistency of a set of defaults . The second addresses reasoning about the default properties of an individual. given a set of default statements . Most extant .work in default reasoning has concentrated on the second area . This paper addresses the first area only. as an initial investigation into the area of default reasoning. The approach is based on adding a "variable conditional" operator to first-order logic. This operator is used to express prototypical. rather than strict . relations between ·entities and properties . A possible worlds semantics is provided for the logic along with a proof theory ; soundness and completeness results are also provided . It is argued that the variable conditional in the logic captures common intuitions concerning defaults and prototypical properties .