Now it's Obvious to The Eye - Visually Explaining XQuery Evaluation in a Native XML Database Management System.
Andreas M. Weiner, Christian Mathis, Theo Härder, Caesar Ralf Franz Hoppen · BTW · 2009
As the evaluation of XQuery expressions in native XML database management systems is a complex task and offers several degrees of freedom, we propose a visual explanation tool—providing an easily understandable graphical representation of XQuery—for tracking the XQuery evaluation process from head to toe.