The increasing volume of data stored as XML documents makes fragmentation techniques an alternative to the performance issues in query processing. Fragmented databases are feasible only if there is a transparent way to query the distributed database. Fragments allow for intra-query parallel processing and data reduction. This paper presents our methodology for XQuery query processing over distributed XML databases. The methodology comprises the steps of query decomposition, data localization, and global optimization. This methodology can be used in an XML database or in a system that publishes homogeneous views of semi-autonomous databases. An implementation has been done and experimental results can achieve performance improvements of up to 95% when compared to the centralized environment.
