Abstract
XML databases have been widely used for web applications to facility data exchanges through internet. Traditional database systems, including XML systems, usually handle precise and well-defined data. In the real world, there exist data that is uncertain and ambiguous. Fuzzy logic reflects human nature to express and evaluate the world in a vague manner. This paper describes our approach of incorporating fuzzy logic into XML database systems. Our system is built on top of an existing XML database management system, which allows the definition and storage of fuzzy data in addition to crisp information. We defined a query language based on the XQuery standard that allows users to query the underlying database using fuzzy expressions. Another important issue in a database system is integrity constraint management. Active rules, also named Event-Condition-Active rules, have mainly been used in relational database systems for integrity control, which are promising features for XML databases. Our fuzzy system includes an active rule-based subsystem that supports the specification and execution of active rules. Users can use fuzzy expressions in the rule definition to declaratively define business logic. The system supports different types of events, including temporal events and composite events, in addition to traditional mutation events.