I tend to use a URIResolver for this sort of thing. The
javax.xml.transform.Source interface does not define a mechanism for
determining the source file location (there may not even be
one) so the
XSL transform has no way of knowing where the XSL file came
from, thus
can't find things relative to it.
On the contrary: Source has a method setSystemId(). Whether or not this is
actually the location of the stylesheet, the value you supply is treated as
the base URI of the stylesheet, and is used to resolve relative URIs within
it.
Michael Kay