Don't know what I mean? Dig this:
Think about it this way: JDOM ships with the Apache Xerces parser. That parser isn't part of JDOM, but is used by JDOM, so it's included to ensure that JDOM is usable out of the box. The same principle applies for JAXP, but it isn't as clearly publicized: JAXP comes with a parser so it can be used immediately. However, many people refer to the classes included in Sun's parser as part of the JAXP API itself. For example, a common question on newsgroups used to be, "How can I use the XMLDocument class that comes with JAXP? What is its purpose?" The answer is somewhat complicated.
First, the com.sun.xml.tree.XMLDocument class is not part of JAXP. It is part of Sun's Crimson parser, packaged in earlier versions of JAXP. So the question is misleading from the start. Second, a major purpose of JAXP is to provide vendor independence when dealing with parsers. With JAXP, you can use the same code with Sun's XML parser, Apache's Xerces XML parser, and Oracle's XML parser. Using a Sun-specific class, then, violates the point of using JAXP. Are you starting to see how this subject has gotten muddied? The parser and the API in the JAXP distribution have been lumped together, and some developers mistake classes and features from one as part of the other, and vice versa.
Who does really want vendor-independence in an XML processing API?