---
title: "Description Logics with Approximate Definitions - Precise Modeling of Vague Concepts"
authors:
  - "Stefan Schlobach"
  - "Michel C. A. Klein"
  - "Linda Peelen"
doi: ""
url: "https://ijcai.org/proceedings/2007/88"
pdf: "https://ijcai.org/proceedings/2007/0088.pdf"
venue: "Proceedings of the Twentieth International Joint Conference on Artificial Intelligence"
year: 2007
pages: "557-561"
track: ""
keywords:
---

# Description Logics with Approximate Definitions - Precise Modeling of Vague Concepts

Stefan Schlobach, Michel C. A. Klein, Linda Peelen

*Proceedings of the Twentieth International Joint Conference on Artificial Intelligence*, pages 557-561.

## Abstract

We extend traditional Description Logics (DL) with a simple mechanism to handle approximate concept definitions in a qualitative way. Often, for example in medical applications, concepts are not definable in a crisp way but can fairly exhaustively be constrained through a particular sub- and a particular super-concept. We introduce such lower and upper approximations based on rough-set semantics, and show that reasoning in these languages can be reduced to standard DL satisfiability. This allows us to apply Rough Description Logics in a study of medical trials about sepsis patients, which is a typical application for precise modeling of vague knowledge. The study shows that Rough DL-based reasoning can be done in a realistic use case and that modeling vague knowledge helps to answer important questions in the design of clinical trials.