Introduction

In this section, we describe how to implement our fuzzy variant of the XPath language with the XQuery language. Basically, we have defined an XQuery library able to fuzzily handle XPath expressions in such a way that our proposed fuzzy XPath can be encoded as XQuery expressions.

The implementation of our fuzzy extension of XPath is based on an XQuery library of functions including deep and down operators as well as the fuzzy operators and+, and-, and, or+, or-, or and avg. Using this library the user can replace Boolean operators by fuzzy versions in XPath expressions, as well as (s)he can call to deep and down operators to obtain ranked sets of answers. The answers are shown with a Retrieval State Value (RSV) representing the degree of satisfaction. They can also ordered with respect to the RSV in XQuery making use of descending expression, as well as filtered with regard to a threshold.

Our approach is not intended to be focused on handle XML documents with fuzzy information. Rather than the input documents in our proposal are XML documents with crisp information, but the answers of a query offers fuzzy information, that is, a RSV of each answer. Therefore our approach is focused on the handling of standard XML documents in which we can retrieve information ranked by a certain degree of satisfaction. In other words, our library can be used from any XQuery processor to query any XML document with crisp information.

Although the input of a query is a crisp XML document, the library assign internally, and in a transparent way to the user a RSV to each of node of interest in the document. The RSVs assigned to each node of interest are used to compute the RSV of the answer.