Butterfly XML - Elegant XML Editor: "The Butterfly XML IDE is built on top of a new real-time incremental XML parsing algorithm. The DOM is updated in real-time as the user types and not in a separate thread. The editor features syntax and error highlighting, incremental validation, intelligent code completion (based on XML Schema, DTD, or document analysis), XSLT pipelines, DTD and Schema Generation, and side by side DOM and source viewing. Built-in support for XHTML, XSL, XForms, XMLSchemas, XSP, and Cocoon sitemaps is included. Support for other XML types can also easily be added. The editor is capable of parsing XML documents that are not well-formed and showing the source of the errors. Errors in documents are highlighted in the source as well as marked inthe DOM view. This allows for easy conversion of HTML to well-formed XML. The side by side DOM and source viewing allows for the tree view ofthe XML to be instantly updated as the user types. The source can also be navigated and updated from the DOM tree. XSLT pipelines make building up and visualizing complex transformations easy."
Version 1.1 has just been released.