I think you've hit a problem that Saxon is not actually checking the
type of supplied stylesheet parameters against their declaration at the
moment. If you are calling Saxon from the command line, then the
supplied parameter is always a string, regardless of the xsl:param
declaration.

The answer is to declare it as a string, and convert it to an integer
using a casting function:

<xsl:param name="pos-as-string"/>
<xsl:variable name="pos-as-integer"
select="xs:integer($pos-as-string)"/>

Michael Kay