<?xml version="1.0"?><book>  <title>Data on the Web</title>  <author>Serge Abiteboul</author>  <author>Peter Buneman</author>  <author>Dan Suciu</author>  <section id="intro" difficulty="easy" >    <title>Introduction</title>    <p>Text ... </p>    <section>      <title>Audience</title>      <p>Text ... </p>    </section>    <section>      <title>Web Data and the Two Cultures</title>      <p>Text ... </p>      <figure height="400" width="400">        <title>Traditional client/server architecture</title>        <image source="csarch.gif"/>      </figure>      <p>Text ... </p>    </section>  </section>  <section id="syntax" difficulty="medium" >    <title>A Syntax For Data</title>    <p>Text ... </p>    <figure height="200" width="500">      <title>Graph representations of structures</title>      <image source="graphs.gif"/>    </figure>    <p>Text ... </p>    <section>      <title>Base Types</title>      <p>Text ... </p>    </section>    <section>      <title>Representing Relational Databases</title>      <p>Text ... </p>      <figure height="250" width="400">        <title>Examples of Relations</title>        <image source="relations.gif"/>      </figure>    </section>    <section>      <title>Representing Object Databases</title>      <p>Text ... </p>    </section>         </section></book>