\chapter{X-tree Indexing}\label{ch:xtrees}

The previous chapter showed that Y and Z queries could not be
answered efficiently using known approaches. In this chapter,
we propose a new indexing scheme and analyse how it can provide
effective query answering for Y and Z queries.

\section{X-trees}

Blah blah blah X-trees blah blah blah.

\section{Indexing effectiveness}

Blah blah blah indexing effectiveness blah blah blah.

