Development of XQuery Interpreter Extensions Based on Fuzzy Logic with Priorities

Abstract

In many real-world applications, information is often imprecise and uncertain. With the popularity of web-based applications, huge amounts of data are available on the web, and XML (eXtensible Markup Language) has become the de facto standard for data exchange over the internet. The XQuery is the language for querying XML data. However, XML and XQuery suffer from incapability of representing and manipulating imprecise and uncertain data. Consequently, this work represents fuzzy data in XML documents and extends XQuery language as providing a more flexible XQuery language by using the fuzzy set theory. In this thesis, an extension of the XQuery query, called Fuzzy XQuery is described. It allows users to define priority, threshold and fuzzy expressions in their queries. Users also can predefine linguistic terms to use them in querying. An algorithm for calculating the global constraint satisfaction degree using the Generalized Prioritized Fuzzy Constraint Satisfaction Problem (GPFCSP) is introduced. Furthermore, Fuzzy XQuery Interpreter (FXI) is implemented allowing execution of fuzzy XQuery queries based on open source technologies and native XML open- source database. Additionally, innovative methods for computing fuzzy set compatibility and introducing order over fuzzy sets have been implemented, which give serious improvements in computational performance compared to previous implementations.