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XML Tutorial

XML HOME XML Introduction XML How to use XML Tree XML Syntax XML Elements XML Attributes XML Namespaces XML Display XML HttpRequest XML Parser XML DOM XML XPath XML XSLT XML XQuery XML XLink XML Validator XML DTD XML Schema XML Server XML Examples

XML AJAX

AJAX Introduction AJAX XMLHttp AJAX Request AJAX Response AJAX XML File AJAX PHP AJAX ASP AJAX Database AJAX Applications AJAX Examples

XML DOM

DOM Introduction DOM Nodes DOM Accessing DOM Node Info DOM Node List DOM Traversing DOM Navigating DOM Get Values DOM Change Nodes DOM Remove Nodes DOM Replace Nodes DOM Create Nodes DOM Add Nodes DOM Clone Nodes DOM Examples

XPath Tutorial

XPath Introduction XPath Nodes XPath Syntax XPath Axes XPath Operators XPath Examples

XSLT Tutorial

XSLT Introduction XSL Languages XSLT Transform XSLT <template> XSLT <value-of> XSLT <for-each> XSLT <sort> XSLT <if> XSLT <choose> XSLT Apply XSLT on the Client XSLT on the Server XSLT Edit XML XSLT Examples

XQuery Tutorial

XQuery Introduction XQuery Example XQuery FLWOR XQuery HTML XQuery Terms XQuery Syntax XQuery Add XQuery Select XQuery Functions

XML DTD

DTD Introduction DTD Building Blocks DTD Elements DTD Attributes DTD Elements vs Attr DTD Entities DTD Examples

XSD Schema

XSD Introduction XSD How To XSD <schema> XSD Elements XSD Attributes XSD Restrictions

XSD Complex

XSD Elements XSD Empty XSD Elements Only XSD Text Only XSD Mixed XSD Indicators XSD <any> XSD <anyAttribute> XSD Substitution XSD Example

XSD Data

XSD String XSD Date XSD Numeric XSD Misc XSD Reference

Web Services

XML Services XML WSDL XML SOAP XML RDF XML RSS

References

DOM Node Types DOM Node DOM NodeList DOM NamedNodeMap DOM Document DOM Element DOM Attribute DOM Text DOM CDATA DOM Comment DOM XMLHttpRequest DOM Parser XSLT Elements XSLT/XPath Functions

DTD - XML Building Blocks


The main building blocks of both XML and HTML documents are elements.


The Building Blocks of XML Documents

Seen from a DTD point of view, all XML documents are made up by the following building blocks:

  • Elements
  • Attributes
  • Entities
  • PCDATA
  • CDATA

Elements

Elements are the main building blocks of both XML and HTML documents.

Examples of HTML elements are "body" and "table". Examples of XML elements could be "note" and "message". Elements can contain text, other elements, or be empty. Examples of empty HTML elements are "hr", "br" and "img".

Examples:

<body>some text</body>

<message>some text</message>

Attributes

Attributes provide extra information about elements.

Attributes are always placed inside the opening tag of an element. Attributes always come in name/value pairs. The following "img" element has additional information about a source file:

<img src="computer.gif" />

The name of the element is "img". The name of the attribute is "src". The value of the attribute is "computer.gif". Since the element itself is empty it is closed by a " /".


Entities

Some characters have a special meaning in XML, like the less than sign (<) that defines the start of an XML tag.

Most of you know the HTML entity: "&nbsp;". This "no-breaking-space" entity is used in HTML to insert an extra space in a document. Entities are expanded when a document is parsed by an XML parser.

The following entities are predefined in XML:

Entity References Character
&lt; <
&gt; >
&amp; &
&quot; "
&apos; '

PCDATA

PCDATA means parsed character data.

Think of character data as the text found between the start tag and the end tag of an XML element.

PCDATA is text that WILL be parsed by a parser. The text will be examined by the parser for entities and markup.

Tags inside the text will be treated as markup and entities will be expanded.

However, parsed character data should not contain any &, <, or > characters; these need to be represented by the &amp; &lt; and &gt; entities, respectively.


CDATA

CDATA means character data.

CDATA is text that will NOT be parsed by a parser. Tags inside the text will NOT be treated as markup and entities will not be expanded.