Hi-- We're working on improving the explanations of these keywords; expect
to see new drafts of XLL soon. In the meantime...
FOLLOWING/PRECEDING (not NEXT/PREVIOUS) refers to the elements (or
pseudo-elements) that start before/after the current one (the "location
source"), anywhere in a document. One way to understand this is to imagine
all the start-tags strung out on a line. Go left to get the PRECEDING
elements of the location source, and go right to get the FOLLOWING elements.
FSIBLING/PSIBLING refers to the elements (or pseudo-elements) before/after
the location source that share the *same parent* as the location source.
So PSIBLING identifies a subset of all PRECEDING elements, and FSIBLING
identifies a subset of all FOLLOWING elements.
I gave an XML/XLL tutorial at the SGML/XML '97 conference, and have put my
PowerPoint slides up on our web site. (They're in .ppt 97 form.) You can
find them at <http://www.arbortext.com/xmlresrc.html> if you'd like to see
the explanation I gave for how the Xpointer addressing keywords work.
Eve