RWTH Aachen University
Element constructor is one of most expensive operations of the XQuery language as it requires deep copy of the nodes which make up the content of the constructed element. In this paper, the authors propose various optimization and implementation techniques to avoid copying of the nodes during constructor evaluation. The proposed techniques are based on using special kind of XQuery constructors with modified semantics which evaluation does not require content node copying. They also provide optimization rules which replace standard constructors with modified ones without changing query result.