What does an XML document look like inside?

<script type="text/javascript">google_ad_client = "pub-8800625213955058";/* 336x280, 创建于 07-11-21 */google_ad_slot = "0989131976";google_ad_width = 336;google_ad_height = 280;//</script><script type="text/javascript"src="http://pagead2.googlesyndication.com/pagead/show_ads.js"></script>The basic structure is very similar to most other applications of SGML, including HTML. XML documents can be very simple, with no document type declaration (DTD), and straightforward nested markup of your own design: Hello, world! Stop the planet, I want to get off!Or they can be more complicated, with a DTD specified (see the question on document types), and maybe an internal subset (local DTD changes in [square brackets]), and a more complex structure:]> hand-colored, presumably by the author Vitam capias Or they can be anywhere between: a lot will depend on how you want to define your document type (or whose you use) and what it will be used for