Saxon

Since this is a run-time error, it would be very useful to have a source document that allows me to reproduce the problem. A small one, ideally!

I think it may be related to the mode=#all template. A streaming apply-templates instruction has selected for processing a template rule that has not been prepared for streaming, and this could be because the mode="#all" rule is causing confusion as to whether it is part of the streamable mode or not.

I still can not get this to work and would be greatful for any help.

I am attaching a slightly modified version of the stylesheet.

It works with streamable="no" but fails with streamable="yes" -- either I ran into the exception above or I get a different result than with streamable="no" (when the stylesheet finishes, the result document looks like it has been transformed by the implicit stylesheet rules only (as if no mode is applied).

The primary problem is the [position() < 3] predicate. Saxon can't currently hande positional predicates when streaming (it doesn't count the nodes and remember how many there have been). I've been doing work in this area in 9.5, but it still can't handle this case - though I shall work on it.

The secondary problem is the absence of diagnostics as to the cause. I'll see if I can fix that in a 9.4 patch.

I think your best bet to implement a streaming solution for this one is probably to use xsl:iterate - this allows you to maintain your own count of how many vf:Data/* elements you have seen, and to do different processing based on the value.

Incidentally, the option -explain:on is often useful with streaming. In this case (before crashing) it outputs the message

Cannot use streaming apply-templates: Cannot convert the expression {subsequence(child::element(), 1, 2)} to a pattern

Which might not be completely user-friendly, but gives a hint as to where the problem lies.

Thanks, I will get back to the stylesheet later today. I don't need the position test at all - I put it there just to get a smaller result for debugging.