You may need functions that are not part of standard XSLT. A number of organizations have defined so-called extension elements that provide these additional functions.
To use an extension, you must add two attributes to the
xslt:stylesheet element of your
Declare a namespace for the extension elements by adding an
attribute of the form
n is the namespace you are
u is the URI of
the extension element's definition.
Tell XSLT to process this namespace, instead of writing it
to the output, by using an attribute of the form
is the same namespace name used in the previous step.
We'll just give one example; more extensions will arise as XSLT evolves.