Abstract
Fuzzy logic reflects human nature to express and evaluate the world in a vague manner. This paper describes our approach to incorporate fuzzy logic into XML database systems. The system was built on top of traditional XML databases, while allows the storage of fuzzy data as well as crisp data. The paper describes the structure of the system, starting with the critical architectural component named fuzzy meta- knowledge base, which records different types of fuzzy distributions for database attributes. Next, a fuzzy query language is presented that is based on the XQuery standard, while allowing fuzzy expressions in any condition in a query. A query processor was built to allow the processing and execution of a fuzzy query over both fuzzy and crisp XML data.