The "Assign working XML file" command assigns an existing XML file to the currently open DTD or schema file.
The XML file is used to preview the XSLT file using the XML data. Clicking the IE Preview tab without having assigned an XML file, opens a message box prompting you to select one.
Please note:
The name and folder of the XML working file is displayed in the title bar of XSLT Designer! If a file has not been assigned, only the *.sps name is displayed.