I've wondered from time to time whether a function such as
document('lookup.xml') should be pre-evaluated at compile time. At present
Saxon doesn't - because it would cause chaos in cases where the contents of
the URL change between compile time and run-time.

Could something like this be compiled into the Templates object? (is it?)

<xsl:param
  name="something"
  select="document('something.xml')"/>

best,
-Rob