"Vex is an editor for XML documents. The "visual" part comes from the fact that Vex hides the raw XML tags from the user, providing instead a wordprocessor-like interface. Because of this, Vex is best suited for "document-style" XML documents such as XHTML and DocBook rather than "data-style" XML documents.
Vex is released under the GNU Lesser General Public License (LGPL), meaning that it will always be free to use, modify, and re-distribute.
Vex uses standard DTD files to define document types and CSS stylesheets to define document layout."