Extending Databases to Precision-Controlled Retrieval of Qualitative Information

Abstract

A hierarchy is an arrangement of qualitative values in a tree with certain properties. Hierarchies allow to define the confusion conf(r, s) in using qualitative value r instead of the intended or correct value s. From here, “predicate P holds for object o”, written P(o), is generalized to “P holds for o within confusion ε”, written P _ε (o). These precision-controlled predicates are useful to retrieve approximate answers, where the error (confusion) is known.

The predicates are implemented through an extended SQL that uses confusion to retrieve information from a database. We show how to extend any database for precision-controlled retrieval. Limiting the total error is also useful, and this is achieved by predicate P^e. Examples are given.