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. ex uses standard DTD files to define document types and CSS stylesheets to define document layout. Vex can be extended with third-party or custom, in-house plugins.