XSLT
Altova website: 
XSLT Editor
This section on XSLT is organized into the following sections:
•Editing XSLT documents: describes the editing support for XSLT documents in XMLSpy
•XSLT Processing: shows the various ways in which XSLT transformations can be carried out in the XMLSpy GUI using engines of your choice. This section also explains important XSLT settings in XMLSpy.
•XSL Outline: describes the XSL Outline and XSL Info Windows, which together provide a powerful way to view, navigate, and manage a collection of XSLT files.
XPath Evaluation
When an XML document is active, you can use the XPath/XQuery Window to evaluate XPath expressions. This is a very useful feature to quickly check how an XPath expression will be evaluated. Type in an XPath expression and specify whether it should be evaluated relative to the document root or to a selected context node in the XML document. The result of the evaluation will be displayed immediately in the XPath/XQuery Window. How to use the XPath/XQuery Window is described in the section GUI and Environment | XPath/XQuery Window.
XSLT Profiler and Debugger
XMLSpy also contains an XSLT Profiler and XSLT Debugger to help you create correct and efficient XSLT stylesheets faster. These two features are described in the section XSLT and XQuery Debugger.
Additional XSLT features
Additional and more detailed information about the various features described in this section is in the descriptions of the relevant menu commands (in the User Reference section).
Altova XSLT Engines
For details about how the Altova XSLT 1.0, 2.0, and 3.0 Engines are implemented, see XSLT and XQuery Engine Information in the Appendices.
RaptorXML for command line and batch processing
The XMLSpy GUI enables batch processing via the projects functionality. However, if you are looking for more flexibility, you should try Altova's RaptorXML product, which provides fast XML validation, XSLT transformation, and XQuery execution functionality. RaptorXML is ideal if you wish to perform XSLT transformations from the command line, or batch processing.