I have the following problem: I have an XML and an XSLT file to process this it and generate output.
The output of this process should contain a control character '0B'. And as far as I know, XML doesn't embed control characters, so how can I accomplish this?
Is the result meant to be an XML file? As you say, XML doesn't allow character U+000B. So by definition, any file containing that character is not a valid XML file. What's the bigger picture here? Why do you need that character? What alternatives might be available to you?
If you're trying to create a text file as the result of the XSLT transformation, that's a different matter.
You could also encode your payload containing 0x0B to Base64 before adding to your XML Document.
This would rely on the consumer of your output transformation being able to convert back from Base64 to the original encoding.
If the relevant XML format supports such characters, I would expect them to reside in some element which supports CDATA.
Can you put your characters inside a CDATA section? XSLT has a construct for creating CDATA sections (<xsl:cdata>). Inside, you can encode your characters using XML entity references <xsl:entity-ref/>.
The parser which reads your XML file should be able to convert those entityrefs to the appropriate characters.