dbfo processing instructions

I can't see any evidence – in the appearance of my PDFs or in the intermediate FO files – that my dbfo PIs are being processed.

For example, my understanding of the following (adapted from Stayton, DocBook XSL, 3rd edn 2005, p274)

<para>Now is the time for all good men</para>

<para><?dbfo background-color="#FFCCCC"?>to come to the aid of the party</para>

is that the former para's background colour will be inherited and the latter's will be pink.

Is there some way in which I might have disabled the processing of PIs?

Thanks in advance

Stephen Taylor