Specifying Attributes

Adding attributes to an existing DTD is easy. For each attribute, you need to specify which element it goes with, what the attribute name is, what type of values it may have, and whether the attribute is optional or not. This information is specified in this model:

  elementName attributeName type optionalStatus
>

To add the maxlength attribute to the </code> element, you write this: </p> <pre><!ATTLIST textarea maxlength CDATA #IMPLIED></pre> <p> The <code>CDATA</code> specification means that the attribute value can contain any old character data you please; thus <code>maxlength="300"</code> or <code>maxlength="ten"</code> will both be valid. For “open-ended” data, DTDs don’t let you get more specific. The <code>#IMPLIED</code> specification means that the attribute is optional. A required attribute would specify <code>#REQUIRED</code>. </p> <p> When you have a list of possible values for an attribute, you may specify them in the DTD. This is the case with the attribute named <code>required</code>, which has the values <code>true</code> and <code>false</code>. The values are case sensitive; in this example only the lowercase values are specified, so a value of <code>TRUE</code> would not be considered valid. </p> <pre><!ATTLIST textarea required (true|false) #IMPLIED></pre> <p> Confusion alert! This attribute is <em>named</em> “required,” but you don’t have to put it on every <code><textarea></code> element, so it’s an optional attribute. </p> <p> The attribute named <code>required</code> should also be available to the <code><input></code> and <code><select></code> elements. All in all, the specifications to modify the DTD look like this: </p> <pre><!ATTLIST textarea maxlength CDATA #IMPLIED><br><!ATTLIST textarea required (true|false) #IMPLIED><br><!ATTLIST input required (true|false) #IMPLIED><br><!ATTLIST select required (true|false) #IMPLIED></pre></div> </article> <div class="hidden md:flex my-10"> <div class="adsclk-slot " data-adsclk-zone="in-article" data-adsclk-w="336" data-adsclk-h="280" style="width:336px;height:280px;margin:0 auto">in-article · 336x280</div> </div> </main> <aside class="hidden lg:block"> <div class="sticky top-[80px] space-y-5"> <div class="adsclk-slot " data-adsclk-zone="content-sidebar-rectangle" data-adsclk-w="300" data-adsclk-h="250" style="width:300px;height:250px;margin:0 auto">content-sidebar-rectangle · 300x250</div> <div class="adsclk-slot " data-adsclk-zone="half-page" data-adsclk-w="300" data-adsclk-h="600" style="width:300px;height:600px;margin:0 auto">half-page · 300x600</div> </div> </aside> </div> </div> </main> <div class="max-w-[1440px] mx-auto px-4"> <div class="hidden md:flex my-10"> <div class="adsclk-slot " data-adsclk-zone="site-footer-leaderboard" data-adsclk-w="728" data-adsclk-h="90" style="width:728px;height:90px;margin:0 auto">site-footer-leaderboard · 728x90</div> </div> </div> <footer class="border-t border-slate-200 bg-slate-50"> <div class="max-w-[1440px] mx-auto px-4 py-10 grid md:grid-cols-4 gap-8 text-sm"> <div class="md:col-span-2"> <div class="flex items-center gap-2.5"> <span class="inline-grid place-items-center w-9 h-9 rounded bg-leaf-500 text-white font-bold">AT</span> <span class="font-semibold text-lg">Academic Tutorials</span> </div> <p class="mt-3 text-ink-700 max-w-md"> 138 tutorials · 616 articles · 1,126 interview Q&A · 991 FAQs · 1,080 books. Free since 2005. </p> </div> <div> <p class="font-semibold text-ink-900 mb-3">Learn</p> <ul class="space-y-2 text-ink-700"> <li><a href="https://academictutorials.com" class="hover:text-leaf-700">Tutorials</a></li> <li><a href="https://academictutorials.com/articles" class="hover:text-leaf-700">Articles</a></li> <li><a href="https://academictutorials.com/interview-questions" class="hover:text-leaf-700">Interview Q&A</a></li> <li><a href="https://academictutorials.com/faqs" class="hover:text-leaf-700">FAQs</a></li> <li><a href="https://academictutorials.com/books" class="hover:text-leaf-700">Books</a></li> </ul> </div> <div> <p class="font-semibold text-ink-900 mb-3">About</p> <ul class="space-y-2 text-ink-700"> <li><a href="https://academictutorials.com/about" class="hover:text-leaf-700">About us</a></li> <li><a href="https://academictutorials.com/contact" class="hover:text-leaf-700">Contact</a></li> <li><a href="https://academictutorials.com/privacy" class="hover:text-leaf-700">Privacy</a></li> <li><a href="https://academictutorials.com/sitemap.xml" class="hover:text-leaf-700">Sitemap</a></li> </ul> </div> </div> <div class="border-t border-slate-200"> <p class="max-w-[1440px] mx-auto px-4 py-4 text-xs text-ink-500"> © 2026 Academic Tutorials · A Phoenix Softwares property. </p> </div> </footer> <script src="https://banners.adsclk.com/loader.js" async defer></script> </body> </html>