I was looking for how to make appear the name of current chapter in a PDF header. This is called "running header".
Found Dave Pawson's site on XSLT, DocBook, and Braille. The FO section contains very serious stuff pretty above all other tutorials!
The running header requires no trick. It's a standard FO feature: define a marker corresponding to current chapter title / whatever (fo:marker) and retrieve it from the header definition (fo:retrieve-*).