The following is a description of the JARs included with JDOM.  
More information about the JARs can be found by reading the files 
accompanying the JARs.  Note that the build scripts (build*) take
care of adding the proper JARs to the path for building.  However
you need to set your classpath properly for runtime execution.


Short summary:

JDK 1.4 includes XML parser and transformation classes, so if you're
using JDK 1.4+ you don't really need to worry about most of the JARs
in this directory.  However, you might want to add xerces.jar and
xml-apis.jar to your classpath so JDOM will use Xerces 2.4.0 instead
of the default JDK parser Crimson 1.1.  You can also use xalan.jar to
use Xalan 2.5_D1 instead of the older Xalan that comes with the JDK.
See below.

For JDK 1.3 and earlier users, you'll want to add xerces.jar,
xml-apis.jar, and xalan.jar to your classpath.  Or you can use any
third party parser too.

All users should add jaxen-core.jar, jaxen-jdom.jar, and saxpath.jar
to their classpath to use the XPath features in JDOM.


Full explanation:

ant.jar
  Used for building JDOM.  The build scripts include it automatically.
  Don't include it in your runtime path.

xerces.jar
xml-apis.jar
	The popular Xerces XML parser.  Place these two JARs at the head of
  your classpath and Xerces will be used as your parser.

xalan.jar
  An XSLT processor.  Included in J2SE 1.4+.  Put this in your 
  classpath if you're doing transforms on older J2SE versions.  To use 
  the newer Xalan with J2SE 1.4+ see 
  http://xml.apache.org/xalan-j/faq.html#faq-N100CB.

jaxen.jar
  This JAR supports the XPath feature of JDOM.  Put it in your classpath
  if you're using XPath.

--

jdom.jar
  This JAR is created during the build process and put in the "build"
  directory.  This contains the org.jdom.* classes, and you should add this
  JAR to your classpath when using JDOM.

