title: What is the usefulness of NMTOKEN and NMTOKENS types?
body: <ol>
  <li><p>The value of <code>NMTOKEN</code> follows the same rules as XML name, except with <code>NMTOKEN</code> any of the allowed characters can be the first character. Unlike XML <code>string</code> type, <code>NMTOKEN</code> values can’t contain any whitespace. Still I fail to see its usefulness.</p>
  <p>So when and why would we use <code>NMTOKEN</code> type instead of a <code>string</code> type?</p>
  </li>
  <li><p><code>NMTOKENS</code> enables us to specify several <code>NMTOKEN</code> values (separated by whitespace) in a single string. This type makes even less sense, since it also allows a value to contain whitespace characters, which essentially means that both <code>NMTOKENS</code> type and <code>string</code> type can hold exactly the same values.</p>
  <p>So when is this type useful?</p>
  </li>
  </ol>