Web Design in a Nutshell, 3rd Edition

XML Basics

Here is a very simple XML document that is marked up with tags I made up to describe the liner notes for my famous end-of-the-year music compilations. (I could call it JenML).

<?xml version="1.0"?>
<compilation >
<title>Oh Baby! Jen's Favorites</title>
<year>2005</year>
<image source="ohbabycover.jpg"/>
<tracklist>
  <track number="1">
     <artist>The Wrens</artist>
     <song>
        <song_title>Hopeless</song_title> from
        <album_title>The Meadowlands</album_title>,
        <label>Absolutely Kosher Records</label>,
        <release_date>2003</release_date>
     </song>
     <comments>I love The Wrens, both musically and personally.</comments>
  </track>
<!--more tracks added here -->
</tracklist>
</compilation>

Certain things about this example should look familiar to anyone who has seen an HTML document. First, it is a plain-text document. As such, it can be created or edited in any text editor. It also uses tags in brackets to indicate the start and end of content elements in the document. Consider this element from the example:

<artist>The Wrens</artist>

The element includes the content (in this case, the character data “The Wrens”) and its markup (the start tag <artist> and end tag </artist>). In XML, tags are case-sensitive, so <ARTIST>, <Artist>, and <artist>would be parsed as three different elements. Elements may contain character data, other elements, or both. Some elements are empty, which means they have no content. <meta/> is an example of an empty element in XHTML. Elements may be clarified or enhanced with ...