PRE_EVALUATE_DOC_FUNCTION (from http://www.saxonica.com/documentation9.0/javadoc/net/sf/saxon/FeatureKeys.html#PRE_EVALUATE_DOC_FUNCTION)
should be set to false so that XSLTs that use document function are able to
pick up changes eg. when using a metadata record from the catalog via
xml.metadata.get it is very desirable that the document function be evaluated
each time the XSLT is run rather than just once at compile time