Report Number: CS-TR-94-1516
Institution: Stanford University, Department of Computer Science
Title: A Framework for Reasoning Precisely with Vague Concepts
Author: Goyal, Nita
Date: May 1994
Abstract: Many knowledge-based systems need to represent vague concepts
such as ``old'' and ``tall''. The practical approach of
representing vague concepts as precise intervals over numbers
(e.g., ``old'' as the interval [70,110]) is well-accepted in
Artificial Intelligence. However, there have been no
systematic procedures, but only ad hoc methods to delimit the
boundaries of intervals representing the vague predicates. A
key observation is that the vague concepts and their interval
boundaries are constrained by the underlying domain
knowledge. Therefore, any systematic approach to assigning
interval boundaries must take the domain knowledge into
account. Hence, in the dissertation, we present a framework
to represent the domain knowledge and exploit it to reason
about the interval boundaries via a query language. This
framework is comprised of a constraint language to represent
logical constraints on vague concepts, as well as numerical
constraints on the interval boundaries; a query language to
request information about the interval boundaries; and an
algorithm to answer the queries. The algorithm preprocesses
the constraints by extracting the numerical information from
the logical constraints and combines them with the given
numerical constraints. We have implemented the framework and
applied it to medical domain to illustrate its usefulness.
http://i.stanford.edu/pub/cstr/reports/cs/tr/94/1516/CS-TR-94-1516.pdf