DTD Introduction

<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta name="keywords" content="xml dtd introduction, cdata sections, duplicate element names, syntax, programming, how to, xml tutorial, extensible markup language, learn xml"> <meta name="Description" content="Learn about Document Type Definitions (DTD) with this free XML tutorial."> <link rel="canonical" href="https://www.quackit.com/xml/tutorial/dtd_introduction.cfm"> <title>DTD Introduction</title> <script src="//ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script> <link rel="shortcut icon" href="/pix/favicon96.png"> <link rel="apple-touch-icon" href="/pix/apple-touch-icon.png"> <link rel="preconnect" href="https://fonts.googleapis.com"> <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin> <link href="https://fonts.googleapis.com/css2?family=Lato:ital,wght@0,400;0,700;1,400&display=swap" rel="stylesheet"> <link href="/common/css/master.45.min.css" rel="stylesheet"> <script async src="https://cdn.fuseplatform.net/publift/tags/2/3499/fuse.js"></script>  <script async src="https://www.googletagmanager.com/gtag/js?id=G-Q3H025ZKLN"></script> <script> window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date()); gtag('config', 'G-Q3H025ZKLN'); </script> </head> <body> <header class="site-header"> <div class="site-header-base"> <div class="site-logo"> <a title="Quackit Homepage" target="_top" href="/"><img src="/pix/quackit_logo_watermark.png" width="87" height="33" alt="Quackit Logo"></a> </div> <button id="site-nav-toggler" class="site-nav-toggler" aria-expanded="false" aria-controls="site-nav"> <span class="sr-only">Toggle navigation</span> ☰ </button> </div> <nav id="site-nav" class="site-nav"> <div class="site-links"> <ul> <li><a href="/"><i class="fa fa-home"></i> <span class="sr-only">Home</span></a></li> <li><a href="/html/">HTML</a></li> <li><a href="/css/">CSS</a></li> <li><a href="/scripting/">Scripting</a></li> <li><a href="/database/">Database</a></li> </ul> </div> <div class="site-search-top"> <form action="/search/" id="cse-search-box-bottom" class="site-search"> <div> <input type="hidden" name="cx" value="partner-pub-6331358926293806:98x0fk-bbgi"> <input type="hidden" name="cof" value="FORID:10"> <input type="hidden" name="ie" value="ISO-8859-1"> <input type="text" name="q" size="20" class="site-search-input"> <button type="submit" name="sa" class="site-search-button"><i class="fa fa-search"></i></button> </div> </form> </div> </nav> </header> <div class="main"> <article class="content"> <h1 class="page-title">DTD Introduction</h1> <div class="ad ad-top">  <div data-fuse="23059883623"></div> </div> <ul class="pager"> <li><a href="/xml/tutorial/xml_cdata.cfm"><i class="fa fa-long-arrow-left" aria-hidden="true"></i> XML CData</a></li> <li><a href="/xml/tutorial/dtd_doctype.cfm">DTD Doctype <i class="fa fa-long-arrow-right" aria-hidden="true"></i></a></li> </ul> <p class="lead">DTD stands for <i>Document Type Definition</i>. A DTD allows you to create rules for the elements within your XML documents. Although XML itself has rules, the rules defined in a DTD are specific to your own needs.</p> <div class="ad">  <div data-fuse="23059883629"></div> </div> <p>So, for an <a href="/xml/tutorial/xml_documents.cfm">XML document</a> to be well-formed, it needs to use correct <a href="/xml/tutorial/xml_syntax.cfm">XML syntax</a>, and it needs to conform to its DTD or schema (we'll cover XML schemas later).</p> <p>The DTD is declared at the top of your XML document. The actual contents of the DTD can be included within your XML document or included in another document and linked to (or both).</p> <h2>Do I Need to Create a DTD?</h2> <p>If you have created your own XML elements, attributes, and/or entities, then you should create a DTD.</p> <p>If you are creating an XML document using pre-defined elements/attributes/entities (i.e. ones that have been created by someone else), then a DTD should already exist. All you need to do is link to that DTD using the <code>DOCTYPE</code> declaration. (We'll cover <code>DOCTYPE</code> soon).</p> <h2>What's in a DTD?</h2> <p>A DTD consists of a list of syntax definitions for each element in your XML document.</p> <p>When you create a DTD, you are creating the syntax rules for any XML document that uses the DTD. You are specifying which element names can be included in the document, the attributes that each element can have, whether or not these are required or optional, and more.</p> <h2>Example DTD</h2> <p>The following example demonstrates what a DTD could look like:</p> <script src="/common/js/codemirror/lib/codemirror.js"></script> <script src="/common/js/codemirror/mode/htmlmixed/htmlmixed.js"></script> <script src="/common/js/codemirror/mode/css/css.js"></script> <script src="/common/js/codemirror/mode/javascript/javascript.js"></script> <script src="/common/js/codemirror/mode/xml/xml.js"></script> <div class="code-only"> <textarea id="example1" autocomplete="off" spellcheck="false"><!ELEMENT tutorials (tutorial)+>
<!ELEMENT tutorial (name,url)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT url (#PCDATA)>
<!ATTLIST tutorials type CDATA #REQUIRED></textarea> </div> <script> var exampleCode1 = CodeMirror.fromTextArea(document.getElementById("example1"), { mode: "htmlmixed", tabMode: "indent", styleActiveLine: false, lineNumbers: false, lineWrapping: true, theme: "q-dark" }); </script> <p>I'll explain the DTD syntax a little later on, but for now, let's look at how to configure your XML document to use a DTD.</p> <ul class="pager"> <li><a href="/xml/tutorial/xml_cdata.cfm"><i class="fa fa-long-arrow-left" aria-hidden="true"></i> XML CData</a></li> <li><a href="/xml/tutorial/dtd_doctype.cfm">DTD Doctype <i class="fa fa-long-arrow-right" aria-hidden="true"></i></a></li> </ul> </article> <div class="sidebar"> <nav> <ul> <li> <h3><a href="/xml/tutorial/" title="">XML Tutorial</a></h3> <ul> <li><a href="/xml/tutorial/about_xml.cfm" title="">About XML</a></li> <li><a href="/xml/tutorial/xml_viewers.cfm" title="">XML Viewers</a></li> <li><a href="/xml/tutorial/xml_editors.cfm" title="">XML Editors</a></li> <li><a href="/xml/tutorial/xml_documents.cfm" title="">XML Documents</a></li> <li><a href="/xml/tutorial/xml_syntax.cfm" title="">XML Syntax</a></li> <li><a href="/xml/tutorial/xml_elements.cfm" title="">XML Elements</a></li> <li><a href="/xml/tutorial/xml_attributes.cfm" title="">XML Attributes</a></li> <li><a href="/xml/tutorial/xml_css.cfm" title="">XML with CSS</a></li> <li><a href="/xml/tutorial/xml_xsl.cfm" title="">XML with XSL</a></li> <li><a href="/xml/tutorial/xml_namespace.cfm" title="">XML Namespace</a></li> <li><a href="/xml/tutorial/xml_local_namespace.cfm" title="">XML Local Namespace</a></li> <li><a href="/xml/tutorial/xml_default_namespace.cfm" title="">XML Default Namespace</a></li> <li><a href="/xml/tutorial/xml_entities.cfm" title="">XML Entities</a></li> <li><a href="/xml/tutorial/xml_creating_entities.cfm" title="">XML Creating Entities</a></li> <li><a href="/xml/tutorial/xml_cdata.cfm" title="">XML CDATA</a></li> </ul> </li> <li> <h3 class="heading-only">DTD</h3> <ul> <li><a href="/xml/tutorial/dtd_introduction.cfm" title="">DTD Introduction</a></li> <li><a href="/xml/tutorial/dtd_doctype.cfm" title="">DTD DOCTYPE</a></li> <li><a href="/xml/tutorial/dtd_internal_dtd.cfm" title="">DTD Internal</a></li> <li><a href="/xml/tutorial/dtd_external_dtd.cfm" title="">DTD External</a></li> <li><a href="/xml/tutorial/dtd_combined_dtd.cfm" title="">DTD Combined</a></li> <li><a href="/xml/tutorial/dtd_fpi.cfm" title="">DTD FPI</a></li> <li><a href="/xml/tutorial/dtd_elements.cfm" title="">DTD Elements</a></li> <li><a href="/xml/tutorial/dtd_element_operators.cfm" title="">DTD Element Operators</a></li> <li><a href="/xml/tutorial/dtd_attributes.cfm" title="">DTD Attributes</a></li> <li><a href="/xml/tutorial/dtd_attribute_default_values.cfm" title="">DTD Attribute Default Values</a></li> <li><a href="/xml/tutorial/dtd_attribute_types.cfm" title="">DTD Attribute Types</a></li> <li><a href="/xml/tutorial/dtd_general_entities.cfm" title="">DTD General Entities</a></li> <li><a href="/xml/tutorial/dtd_parameter_entities.cfm" title="">DTD Parameter Entities</a></li> <li><a href="/xml/tutorial/dtd_embedded_images.cfm" title="">DTD Embedded Images</a></li> </ul> </li> <li> <h3 class="heading-only">XSLT</h3> <ul> <li><a href="/xml/tutorial/xslt_introduction.cfm" title="">XSLT Introduction</a></li> <li><a href="/xml/tutorial/xslt_example.cfm" title="">XSLT Example</a></li> <li><a href="/xml/tutorial/xslt_syntax.cfm" title="">XSLT Syntax</a></li> <li><a href="/xml/tutorial/xslt_template.cfm" title="">XSLT <template></a></li> <li><a href="/xml/tutorial/xslt_apply-templates.cfm" title="">XSLT <apply-templates></a></li> <li><a href="/xml/tutorial/xslt_value-of.cfm" title="">XSLT <value-of></a></li> <li><a href="/xml/tutorial/xslt_for-each.cfm" title="">XSLT <for-each></a></li> <li><a href="/xml/tutorial/xslt_sort.cfm" title="">XSLT <sort></a></li> <li><a href="/xml/tutorial/xslt_if.cfm" title="">XSLT <if></a></li> <li><a href="/xml/tutorial/xslt_choose.cfm" title="">XSLT <choose></a></li> </ul> </li> <li> <h3 class="heading-only">XPath</h3> <ul> <li><a href="/xml/tutorial/xpath_introduction.cfm" title="">XPath Introduction</a></li> <li><a href="/xml/tutorial/xpath_location_path.cfm" title="">XPath Location Path</a></li> <li><a href="/xml/tutorial/xpath_location_path_absolute.cfm" title="">XPath Location Path - Absolute</a></li> <li><a href="/xml/tutorial/xpath_location_path_relative.cfm" title="">XPath Location Path - Relative</a></li> <li><a href="/xml/tutorial/xpath_attributes.cfm" title="">XPath Attributes</a></li> <li><a href="/xml/tutorial/xpath_axis.cfm" title="">XPath Axis</a></li> <li><a href="/xml/tutorial/xpath_node_test.cfm" title="">XPath Node Test</a></li> <li><a href="/xml/tutorial/xpath_predicate.cfm" title="">XPath Predicate</a></li> <li><a href="/xml/tutorial/xpath_node_set.cfm" title="">XPath Node Set</a></li> <li><a href="/xml/tutorial/xpath_comparison_operators.cfm" title="">XPath Comparison Operators</a></li> <li><a href="/xml/tutorial/xpath_boolean_operators.cfm" title="">XPath Boolean Operators</a></li> <li><a href="/xml/tutorial/xpath_number_operators.cfm" title="">XPath Number Operators</a></li> <li><a href="/xml/tutorial/xpath_string_functions.cfm" title="">XPath String Functions</a></li> <li><a href="/xml/tutorial/xml_tutorial_summary.cfm" title="">Tutorial Summary</a></li> </ul> </li> </ul> </nav> <div class="ad ad-left">  <div data-fuse="23059511712"></div> </div> </div> <div class="ads"> <div class="ad ad-right">  <div data-fuse="23059883626"></div> </div> </div> </div> <div class="searchbox-bottom"> <form action="/search/" id="cse-search-box-bottom" class="site-search"> <div> <input type="hidden" name="cx" value="partner-pub-6331358926293806:npmuvy-i8kk"> <input type="hidden" name="cof" value="FORID:10"> <input type="hidden" name="ie" value="ISO-8859-1"> <input type="text" name="q" size="30" class="site-search-input"> <button type="submit" name="sa" class="site-search-button"><i class="fa fa-search"></i></button> </div> </form> <script src="//cse.google.com/cse/brand?form=cse-search-box-bottom&lang=en"></script> </div> <footer> <p class="about"><a href="/"><i class="fa fa-home"></i> Home</a> | <a href="/about.cfm" rel="nofollow">About</a> | <a href="/contact.cfm" rel="nofollow">Contact</a> | <a href="/terms_of_use.cfm" rel="nofollow">Terms of Use</a> | <a href="/privacy_policy.cfm" rel="nofollow">Privacy Policy</a></p> <p>© Copyright 2000 - 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DTD Introduction