Weakening of fuzzy relational queries: an absolute proximity relation-based approach

In this paper we address the problem of query failure in the context of
flexible querying. We propose a fuzzy set–based approach for relaxing
queries involving gradual predicates. This approach relies on the notion
of proximity relation which is defined in an absolute way. We show
how such proximity relation allows for transforming a given predicate
into an enlarged one. The resulting predicate is semantically not far
from the original one and it is obtained by a simple fuzzy arithmetic
operation. The main features of the weakening mechanism are
investigated and a comparative study with some methods proposed for
the purpose of fuzzy query weakening is presented as well. Last, an
example is provided to illustrate our proposal in the case of conjunctive
queries.