| Microsoft XML Core Services (MSXML) 5.0 for Microsoft Office - XSLT Developer's Guide |  |
Supported XSLT Features
The implementation of MSXML 5.0 is in full compliance with the XSL Transformations (XSLT) Version 1.0 W3C Recommendation, 16 November 1999, and with the XML Path Language (XPath) Version 1.0 W3C Recommendation, 16 November 1999.
In addition, MSXML 5.0 maintains backward compatibility with the MSXML 2.0 and 2.5 implementations of Section 2 of the December 1998 XSL Working Draft of the Extensible Stylesheet Language (XSL). It does no support XSL formatting objects.
Note For information about support for XSL, see the MSXML 2.5 documentation available at MSDN®.
Where the XSLT recommendation provides a fallback behavior in cases of error (for example, two matching templates with the same priority), MSXML performs the fallback behavior.
MSXML provides two mechanisms for implementing extension functions: embedded script implementations (<msxsl:script>) and external objects (addObject). MSXML does not provide a mechanism for implementing extension elements.
See Also
addObject Method | msxsl:script Element
Other Resources 
XML SDK 2.5 Documentation | XSL Transformations (XSLT) Version 1.0 | XML Path Language (XPath) Version 1.0