In the following draft version of XSL 2.0
http://www.w3.org/TR/xslt20/#element-output
there is this instruction:
<!-- Category: instruction -->
<xsl:result-document
...
and
<!-- Category: declaration -->
<xsl:output
...
In my opinion there should be something that instructs the
processor to overwrite or concatenate the result to external
file.
If appending to a file were allowed, the results of the stylesheet would
depend on the order of execution of instructions. XSLT is designed to
avoid such dependencies.
There is however an instruction xsl:message. It is documented that the
order in which messages are output is implementation-defined.
Implementors can provide control over the destination of xsl:message,
allowing it to be used for the kind of logging applications you
describe. This can be done with XSLT 1.0 - it doesn't even need any XSLT
2.0 enhancements (though in the Saxon implementation, appending the
results of xsl:message to a file does require you to write some Java
code).
Michael Kay
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list