Doing an XSL transform of a branch of a Docbook element tree

Answer 1

Instead of trying to apply the DocBook XSL stylesheet to a single element, you could apply it to the full document, but specify the part of the document you want to transform with the rootid parameter.

From the reference documentation:

The entire document will be loaded and parsed, but formatting will begin at the element identified, rather than at the root. For example, this allows you to process only chapter 4 of a book.

Because the entire document is available to the processor, automatic numbering, cross references, and other dependencies are correctly resolved.