An Implementation Approach for XQuery Based on Lazy Evaluation

In order to accelerate the execution of XQuery, this paper introduces an evaluator named as XML query lazy evaluator (XQLE), which uses lazy evaluation optimization technique. The input language is functional XML query language (FXQL) that is a functional language with concise form. For data model, XQLE uses generalized list with the ability to hold closure and XML node to support lazy calculation of list node. Under lazy mode, the overhead of acquiring the data that has no relationship to the final result of calculation can be eliminated. Finally, we use a lot of example programs to show the lazy evaluator has better performance compared with eager evaluator in the average execution speed.