Q42 is showing off a demo of their Xopus editor, which allows developers to edit XML inside of a browser context.

The Xopus editing environment:

"is a generic in-browser XML editor that takes any combination of XML, Schema (XSD) and XSL and makes it directly editable. It works in any XML/XSL-enabled browser. (currently only Microsoft Internet Explorer 5.5 on the Microsoft Windows platform)"

Xopus combines XML, XML Schema, and XSLT with Dynamic HTML and JavaScript to manage the in-browser editing experience, and Q42's explanation also discusses integration with the MMbase content management system.