anchor.diff:  
   *HTML element*: +<section>+
   
  -*Attribute requirements*: +class="preface"+, +class="foreword"+, or +class="introduction"+, depending on content
  -
  -*Content model*: First child must be +<h1>+ that contains preface title; then zero or more +<h2>+ elements for subtitle content; then zero or more Block Elements; then zero or more Sect1 children (+<section class="sect1">+)
  -
  -*Example*
  -
  -----
  -<section class="preface">
  +*Attribute requirements*: +data-type="preface"+, +data-type="foreword"+, or +data-type="introduction"+, depending on content
  +
  +*Content model*: First child must be +<h1>+ that contains preface title; then zero or more +<h2>+ elements for subtitle content; then zero or more Block Elements; then zero or more Sect1 children (+<section data-type="sect1">+)
  +
  +*Example*
  +
  +----
  +<section data-type="preface">
     <h1>Preface Title</h1>
     <p>Preface content</p>
  -  <section class="sect1">
  +  <section data-type="sect1">
       <!-- Section content here... -->
     </section>
   </section>
  
positive.code: == HTMLBook Specification: Working Draft 19 April 2013
  
  Requirements for HTML5 elements in the HTMLBook specification are below. Special semantic inflections for +class+ attributes, unless otherwise noted, come from http://idpf.org/epub/vocab/structure/[EPUB 3 Structural Semantics Vocabulary]
  
  Many content models refer to "Block elements" or "Inline elements"; please see <<block_elements, Block Elements>> and <<inline_elements, Inline Elements>> for the corresponding list of HTML5 elements that belong to each of these categories.
  
  If no content model or attribute requirements are explicitly specified, then HTMLBook adopts the corresponding requirements in the http://www.w3.org/html/wg/drafts/html/master/[HTML5 Specification]
  
  === Book Component elements
  
  ==== Book
  
  *HTML element*: +<body>+
  
  *Attribute requirements*: +class="book"+ footnote:[Not in EPUB 3 Structural Semantics Vocabulary; from DocBook]
  
  *Content model*: First child must be +<h1>+ that contains book title; then zero or more +<h2>+ elements for subtitle content; then one or more Book Component elements as children (+<div>+ for Part elements, +<nav>+ for Table of Contents, and +<section>+ elements for all other book divisions)
  
  
negative.code: 
  *HTML element*: +<section>+
  
  *Attribute requirements*: +data-type="index"+
  
  *Content model*: First child must be +<h1>+ that contains index title; then zero or more +<h2>+ elements for subtitle content; then zero or more Block Elements; then zero or more Sect1 children (+<section data-type="sect1">+)
  
  *Best practices*: HTMLBook recommends following the http://www.idpf.org/epub/idx/[EPUB Indexes specification] and using ++<ol>++/++<li>++ elements for marking up index entries, with +data-type+ attributes used for semantic inflection as appropriate, but none of this is a formal spec requirement
  
  *Example*
  
  ----
  <section data-type="index">
    <h1>Index Title</h1>
    <div data-type="index:group">
      <h2>A</h2>
      <ol>
        <li data-type="index:term">AsciiDoc, <a href="ch01#asciidoc" data-type="index:locator">All about AsciiDoc</a>
  	<ol>
             <li data-type="index:term">conversion to HTML, <a href="ch01#asctohtml" data-type="index:locator">AsciiDoc Output Formats</a></li>
           </ol>
        </li>
        <li data-type="index:term">azalea, <a href="ch01#azalea" data-type="index:locator">Shrubbery</a></li>
      </ol>
    </div>
  </section>
  