Saxon

The extension function saxon:discard-document() makes multiple updates to data held by the Controller, in particular the document pool and the list of unavailable documents. The method should be synchronized in case there are multiple simultaneous calls to saxon:discard-document() in different threads.

Ideally we should also provide a function that combines the effect of doc() and discard-document() -- and perhaps doc-available() -- all within a single call having atomic effect, but meanwhile simply synchronising discard-document() will remove some potential dangers.

(This is relevant only when transformations are executing in multiple threads, typically as a result of using xsl:result-document).