Microsoft Office XML Editor

msoXmlEd.exe

Inorder for the mso-application processing instruction to work correctl when users open files in Windows Explorer
The XML file typemust be associated with the Microsoft office XML Editor

Excel qualifies the names of the XML nodes with namespaces from the Microsoft Office schemas.
A workbook defines the following namespaces:
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xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
This is the default namespace

Allows you to use the ss abbreviation to prefix the workbook nodes in your XSLT file.

Example - XSLT to ???