XML
This section describes how to work with XML documents in XMLSpy. It covers the following aspects:
•How to create, open, and save XML documents. In this section, some important XMLSpy settings relating to file creation are also explained.
•XML documents can be edited in Text View, Grid View, and Authentic View. You can select the view that is most useful for you and switch among the views while editing. Each of the views offers different advantages.
•You can easily and quickly add XML fragments to your XML document from external sources.
•How to use the various XML validation features of XMLSpy.
•Entry helpers for XML documents have certain specific features, and these are described.
•How to process XML documents with XSLT and XQuery. Various XMLSpy features related to processing are explained. A section on PDF Fonts explains how fonts are processed when generating PDF output.
•Miscellaneous other features for working with XML documents are described.
Altova website: 
XML Editor