I do the following

<xsl:include href="functions/f_FunctionName.xsl" />

Quoting Craig Sampson <Craig.Sampson@xxxxxxx>:

>  I've written a saxon:function that I want to include in several different
> stylesheets. The function works when I physically add it to my stylesheet
> like so:
> 
> <xsl:stylesheet ...>
> 
> <xsl:include href="a"/>
> <xsl:include href="b"/>
> 
> <xsl:template ...
> 
> <saxon:function name="func:c">
>  ...
>  <saxon:return ...>
> </saxon:function>
> 
> </xsl:stylesheet>
> 
> 
>  But I haven't been able to work out how to include the function if it's
> externalized in another file. 
>  Does anyone have a snippet of code that illustrates how I can include it or
> reference it as a separate file.
> 
> Thanks,
>  Craig Sampson