A JSP document is a JSP page written in XML syntax as opposed to the standard syntax described in Chapter 4. Because it is written in XML syntax, a JSP document is also an XML document and therefore gives you all the benefits offered by the XML standard:
You can author a JSP document using one of the many XML-aware tools on the market, enabling you to ensure that your JSP document is well-formed XML.
You can validate the JSP document against a document type definition (DTD).
You can nest and scope namespaces within a JSP document.
You can use a JSP document for data interchange between web applications and as part of a compile-time XML pipeline.
In addition to these benefits, the XML syntax gives the JSP page author ...