Creating navigation menus, breadcrumbs, and hierarchical tables of contents (TOCs) in DITA XML is essential for organizing and structuring your documentation for users. Here’s how you can use links and elements to achieve these navigational aids:

1. Navigation Menus: You can create navigation menus in DITA by using links within your topics. For instance, if you want to create a horizontal or vertical menu to help users navigate between sections of your documentation, you can use links and lists. Each menu item can be linked to a specific topic or section, allowing users to easily access the content they need. You can format the menu using HTML and CSS to achieve the desired visual style.

2. Breadcrumbs: Breadcrumbs provide users with a trail of links that show the path they’ve taken within your documentation. To create breadcrumbs in DITA, you can insert links within your topics that represent each level of the hierarchy. These links are usually placed at the top or bottom of the content, making it easy for users to retrace their steps or jump to a higher-level section. Breadcrumbs are a valuable aid in user navigation and orientation.

3. Hierarchical TOCs: DITA allows you to create hierarchical tables of contents (TOCs) that provide a structured overview of your documentation. You can use the <toc> element to define the TOC structure, including which topics or sections to include and their hierarchical organization. Links within the TOC entries point to the corresponding topics, enabling users to jump directly to the relevant content. Hierarchical TOCs are particularly useful for documentation that has multiple levels of sections and subtopics.

<!-- Example of navigation menu, breadcrumbs, and hierarchical TOC in DITA -->
<div class="menu">
  <ul>
    <li><a href="#section-1">Section 1</a></li>
    <li><a href="#section-2">Section 2</a></li>
    <li><a href="#section-3">Section 3</a></li>
  </ul>
</div>

<section id="section-1">
  <title>Section 1</title>
  <p>Content of Section 1.</p>
</section>

<section id="section-2">
  <title>Section 2</title>
  <p>Content of Section 2.</p>
</section>

<section id="section-3">
  <title>Section 3</title>
  <p>Content of Section 3.</p>
</section>

<p class="breadcrumbs">
  <a href="#home">Home</a> >
  <a href="#section-1">Section 1</a> >
  <a href="#section-2">Section 2</a> >
  <a href="#section-3">Section 3</a>
</p>

<toc>
  <title>Table of Contents</title>
  <tocentry>
    <topicref href="#section-1"/>
  </tocentry>
  <tocentry>
    <topicref href="#section-2"/>
  </tocentry>
  <tocentry>
    <topicref href="#section-3"/>
  </tocentry>
</toc>

In this example, we have a navigation menu, breadcrumbs, and a hierarchical TOC created using links and HTML/CSS formatting. These navigational aids enhance the user experience by making it easier for readers to find and explore the content in your DITA documentation.