Abstract
The creation, maintenance and disposal of tree fragments during XQuery execution form a significant issue in the design of XQuery processors. The problem is further complicated by the definition of node identity which violates the functional nature of the XQuery language.
This paper presents a novel mathematical model of XQuery execution that reflects temporary tree construction and manipulation, including navigation. Using this model as reference, an efficient algorithm of static analysis is presented that determines the level of information required at a particular place of the XQuery program.
As a side effect, the algorithm also decides on the ordered/unordered context as defined by the XQuery language. Based on this algorithm, the amount of information stored during the execution as well as the complexity of operations may be significantly reduced.