The xsl:import element is always used at the top level of the stylesheet, and it must
appear before all other elements at the top level. It has a
mandatory href attribute, which is a URL (absolute or relative) of another stylesheet
to be textually included within this one. The top-level elements of the included stylesheet
effectively replace the xsl:import element.
The xsl:import element may also be used at the top level of the included stylesheet, and so
on recursively.
The elements in the imported stylesheet have lower precedence than the elements in the importing stylesheet. The main effect of this is on selection of a template when xsl:apply-templates is used: if there is a matching template with precedence X, all templates with precedence less than X are ignored, regardless of their priority.
