Whats the logic? Navigation Control

The Navigation Control Center (ncc.html)

The user may intervene with the linear sequential presentation provided by the SMIL files alone.

To do this, the user activates a link in the ncc.html document. The Navigation Control Center contains a series of links to certain positions of the SMIL presentation.


[...]
<h1 class="title">
  <a href="dtb_1.smil#par1">Title</a>
</h1>
<span class="page-normal">
  <a href="dtb_1.smil#par2">1</a>
</span>
<h2>
  <a href="dtb_2.smil#par1">Chapter 1</a>
</h2>
<h2>
  <a href="dtb_3.smil#par1">Chapter 2</a>
</h2>
[...]

Note how the links in ncc.html use a URI that contains not only the name of the SMIL file, but also (following the # character) a fragment of that smil file. The target fragment is always the value of an id attribute in the SMIL file.

If you do not remember or know what a URI is, you are advised to read the URI section in the XHTML grammar overview.