oXygen is an XML editor that supports any XML document, and works with XML Schemas, DTDs, Relax NG schemas, and NRL Schemas. It has powerful transformation support that allows you to edit XSLT and XSL-FO documents and to obtain documents in the desired output format (such as HTML, PS, or PDF) with just one click. It also includes a complete Subversion client, support for flattening XML Schemata, an XML Schema instance generator, integration with the X-Hive/DB, MarkLogic and TigerLogic XML databases, editing actions on the diagram, and a rename refactoring action.
Syntext Serna is a highly customizable, multi-platform, pure XSL-driven WYSIWYG XML content editor. It looks and works like a conventional word processor, yet it gives you much more flexibility to alter or reuse content while keeping its integrity intact. It lets you collaborate on compound documents that contain embedded data from various sources. Content is viewed as an integrated whole that is intuitively transparent to authors.