Common (exsl)

XSLT/XPath Reference: XSLT elements, EXSLT functions, XPath functions, XPath axes

The EXSLT Common package provides basic functions that expand upon the capabilities of XSLT. The namespace for the Common package is http://exslt.org/common.

exsl:node-set(): exsl:node-set() returns a node-set from a result tree fragment, which is what you get when you look at the xsl:variable instead of its select attribute to fetch a variable's value. This lets you process the XML created within a variable to process it in multiple steps.
exsl:object-type(): exsl:object-type() returns a string that indicates the type of the specified object.