For those of you out there looking for a professional XML editor, here a short list of some of the most popular ones at the moment.
Oxygen XML Editor – this is definitely one of the most popular and feature heavy of the XML editors out there. It is supported on all three of the major platforms, has an XSLT debugger, and also can be run as a plugin for Eclipse (which is hugely popular itself). It also has the ability to edit files other than XML and XSL files such as CSS and HTML files, which would be very handy, given the typical usage for XML files in web environments.
Liquid XML Editor – This editor is very similar to Oxygen featurewise, but this editor is only available for the Windows platform, which clearly limits a lot of its customer base. Regardless of that, if for some reason you are running Windows, then this may be the editor for you.
Serna-free – This is an open-source editor available on the Syntex website. This editor is also available for all of the major platforms, but unlike the other editors does not have the ability to edit not XML files. They also have an enterprise version available for download.
Go out and take a look at some of these editors and see which one works for you (all of them have free trial versions for download).
http://www.oxygenxml.com/
http://www.liquid-technologies.com/xml-editor.aspx
http://www.syntext.com/products/serna-free/
