What Serna Is
Syntext Serna is a WYSIWYG XML editor, almost like a conventional word processor. Serna is designed for WYSIWYG document presentation: XML documents can be viewed in print-like appearance without even XML markup tags, if you wish.
In WYSIWYG mode, you are free to change the document tree under the root element. Besides, you can change and remove entity declarations. So when you find yourself desiring to switch to XML markup mode or to Text mode (pure XML code mode), please be aware that there should be an easy way of handling the same use-case in WYSIWYG mode. However, you can use Text mode for specific cases like changing the DOCTYPE declaration or the root element of a document, which is not allowed in WYSIWYG mode.
Every document opened or created in Serna is associated with a particular document type. Depending on the document type and the authoring mode, you get a particular graphical user interface of Serna and the view of the document in the Editing Window.
What Serna Is Not
Serna is not an XML development environment. You will not find it convenient for coding, say, XSL stylesheets or XML schemas. The nice appearance of XML documents like DITA, Docbook and TEI is exactly what Serna is designed for.