Here are three terms that appear throughout the XML literature and
may stymie the XML beginner:
The descriptions of an element that are part of the initial start
tag. To reuse a previous example, in <img
src="picture.jpg" />, src="picture.jpg"
is an attribute for this element. There is some controversy
in the XML world about when to use the contents of an element and
when to use attributes. The best set of guidelines on this particular
issue can be found at http://www.oasis-open.org/cover/elementsAndAttrs.html.
The term CDATA (Character Data) is used in two contexts. Most of the
time it refers to everything in an XML document that is not markup
(tags, etc). The second context involves CDATA
sections. A CDATA section is declared to indicate that an
XML parser should leave that section of data alone even if it
contains text that could be construed as markup.
Tim Bray's annotation of the XML specification (mentioned
earlier) gives the following definition:
The string PCDATA itself stands for "Parsed Character
Data." It is another inheritance from SGML; in this usage,
"parsed" means that the XML processor will read this text
looking for markup signaled by < and
You can think of this as data composed of CDATA and potentially some
markup. Most XML data falls into this classification.
XML has a bit of a learning curve. This small tutorial should help
you get started.
Copyright © 2001 O'Reilly & Associates. All rights reserved.