comicpress-core/docs/en_US/storyline-basics.html

<h1>Storyline Basics</h1>

<p>
  A word before you go any further: For <em>ComicPress Core</em> to work properly, <strong>posts can only be in one category!</strong>
  <em>ComicPress Core</em> will reject any post in more than one category. If you want to put your posts in additional taxonomies, <strong>use tags</strong>.
</p>

<h2>Child Category Ordering</h2>

<p>
  A <strong>storyline</strong> in <em>ComicPress Core</em> parlance is a set of ordered, structured categories.
  By default, categories in WordPress maintain only parent to child relationships &mdash; a category knows if it has a parent, and what that parent is. See the category list below:
</p>

<ul>
  <li><strong>My Comics</strong> has no parent. It's at the root of the hierarchy.</li>
  <ul>
    <li><strong>My Funny Comic</strong> has a parent. It's the <em>My Comics</em> category.</li>
    <ul>
      <li><strong>Chapter One</strong> has a parent. It's the <em>My Funny Comic</em> category.</li>
    </ul>
    <li><strong>My Serious Comic</strong> has a parent. It's the <em>My Comics</em> category.</li>
  </ul>
</ul>

<p>
  While WordPress stores parent/child relationships, it does not store the order of all of the children underneath of a parent (the siblings). It always sorts them alphabetically by name.
  This is bad for Websites that want to run structured sequential creative works, as that means you'd have to name your categories in a way that would cause them to sort
  alphabetically, making the names nonsensical:
</p>

<ul>
  <li><strong>My Comics</strong> will be first, because it has no siblings.</li>
  <ul>
    <li><strong>01: My Funny Comic</strong> will sort first, because <em>01</em> is less than <em>02</em>.</li>
    <ul>
      <li><strong>01: Chapter One</strong> will be first, because it has no siblings.</li>
    </ul>
    <li><strong>02: My Serious Comic</strong> will sort second, because <em>02</em> is greater than <em>01</em>.</li>
  </ul>
</ul>

<p>
  <em>ComicPress Core</em> allows you to sort your categories in any order, and that order is stored within <em>ComicPress Core</em>'s own configuration.
  This would allow you to ensure that <strong>My Funny Comic</strong> always appears before <strong>My Serious Comic</strong>,
  no matter how many children <strong>My Comics</strong> has.
</p>

<h2>Extending WordPress to Know About Sort Ordering</h2>

<p>
  In order for theme developers to be able to access this sort ordering information, <em>ComicPress Core</em> provides two template tags called <code>SL()</code> and <code>SC()</code>
  to retrieve information about the structure of categories. It's a much richer interface than WordPress's provided interface, because they always return hierarchical information:
</p>

<pre class="prettyprint lang-php">
foreach (SL() as $category_id => $info) {
  $category = get_category($category_id);
  printf('Category %d is %d levels deep', $category->name, $info['level']);
}

// by default, SC() returns categories relative to the current post
$next = SC('next');
$previous = SC('previous');
$parent = SC('parent');

// or you can provide a category to be relative to
$next_from_three = SC('next', 3);
$previous_to_chapter_four = SC('previous', 'chapter-four');
</pre>

<h2>Finding and Using Posts</h2>

<p>
  Since <em>ComicPress Core</em> knows about the structure of your storyline, you can use <em>ComicPress Core</em>'s advanced post search template tags to search subsets of your categories.
  This is where a cool interactive goes that illustrates this complex process.
</p>