XMLmind XML Editor (XXE for short) is an XML editor designed for production use. Unlike many other XML editors, its user interface does not allow to do simple things such as:
Open an XML document in the editor and, after this, use a dialog box to associate a DTD and/or a style sheet to the newly opened document.
Select a DTD or schema using a file chooser and then, use another dialog box to select the root element of a new document (conforming to the chosen DTD or schema).
The above features are useful if you muse with an XML file from time to time. They are almost never needed in production use, for example, writing a book ten hours a day.
Out of the box, XXE can be used to author XHTML, DocBook and DITA documents with a good personal productivity.
But if you need to achieve excellent productivity for a group of users in your organization or if you need to use a proprietary DTD, W3C XML Schema or RELAX NG schema, then you'll have to customize existing XXE configurations or you'll have to write a custom configuration for your proprietary schema from scratch.
In an organization, the task of writing a configuration file for XXE is ideally performed by a single person, who belongs to the group of XML authors, but who is specially motivated by becoming the local guru.
The local guru really needs to understand the job of the group of XML authors which will use XXE.
The local guru does not need to be a programmer, or even a member of the IT staff.
If you don't have a person with the profile of a local guru, you may consider hiring an external consultant for a few days.