An option is available in the Configuration to indicate that calls to the doc()
or document() functions with constant string arguments should be evaluated when a query or
stylesheet is compiled, rather than at run-time. This option is intended for use when a reference or lookup
document is used by all queries and transformations. Using this option has a number of effects:
The URI is resolved using the compile-time URIResolver rather than the run-time URIResolver
The document
is loaded into a document pool held by the Configuration, whose memory is released only when
the Configuration itself ceases to exist;
all queries and transformations using this document share the same copy;
any updates to the document that occur between compile-time and run-time have no effect.
The option is selected by using Configuration.setConfigurationProperty()\
or TransformerFactory.setAttribute() with the property name FeatureKeys.PRE_EVALUATE_DOC_FUNCTION.
This option is not available from the command line because it has no useful effect with a single-shot
compile-and-run interface.
This option has no effect if the URI supplied to the doc() or document() function
includes a fragment identifier.
It is also possible to preload a specific document into the shared document pool from the Java application
by using the call
config.getGlobalDocumentPool().add(doc, uri). When the doc() or document()
function is called, the shared document pool is first checked to see if the requested document is
already present. The DocumentPool object also has a discard() method which causes the document
to be released from the pool.
