>  1. Catchwords
>  The Guidelines' section 18.3 (Headers, Footers, and Similar Matter)
>  states that
>      "As a rule, matter associated with the page break (signature,
>      catchword, page number) should be drawn into the PB element as
>      attributes: see section 6.9, Reference Systems."
>  However, in section 6.9 I can't find anything about how to draw a
>  catchword, for instance, into the PB element. I would prefer doing
>  this to using the FW element.

The fact that section 18.3 refers to section 6.9 (id "COrs"), and it
doesn't have the promised discussion is an error that should be
reported to the editors. Luckily, they read this list. Now, to your
underlying question.

For a long time in our early history the WWP did "draw" catchword,
sigature, and page number information into our pagebreak empty
element, PGBK:
     <pgbk catch="rampart" n="17" sig="B3r">
In fact, PGBK also had a left= attribute for backwards- or left-
sided-catchwords, and pgnoalign= with which to indicate whether the
page number (the value of n=) had been left-, center-, or right-
aligned in the original.

This became quite unsatisfactory. First and foremost, no phrase-level
(or other :-) elements could be used inside the catchword or
signature. (Thus the need for pgnoalign=, as one couldn't specify a
rend= attribute for just the page number, not the catchword.) While
we didn't think this was a big deal for elements like NAME, which
aren't needed in catchwords anyway, it did mean
*   No way to insert a SIC element, which might be *very* important
     to us
*   No way to insert a GAP (we didn't call it GAP back then) if some
     characters were unreadable
*   No way to indicate rendition (other than adding more attributes
*   No way, other than inventing conventions for use within the
     CDATA attributes to indicate discrepancies between what signature
     or page number you were on vs what was printed on that page.
     (E.g., no SGML encoded method to indicate that although this is
     what should be refered to as A3v, it wasn't written on the page.)

For a short while I advocated moving these things into a page-break
element with content:
     <pgbk n="19">
         <fw type="pageNum" rend="align(left)">17.</fw>
         <fw type="signature" n="B3r">B3</fw>
         <fw type="catchword">rampa<sic corr="n">r</sic>t</fw>

Our current encoding practice is to encode the pagebreak itself as a
PB element, with the various associated information mostly in
MILESTONE and MW elements (MW is FW renamed for "meta-work", as we
use it for things that were not on the forme, e.g., list heads that
are repeated after a page break, or line numbers in a poem). E.g.
(copied-and-pasted from one of our files):
     <mw type="sig" rend="align(center)">B2</mw>
     <mw type="catch" rend="break(no)align(right)">And</mw>
     <pb n="004">
     <milestone unit="sig" n="B2v">
     <mw type="pageNum" rend="align(left)">4</mw>
This PB occurs between pages 3 and 4. The signature and catchword
appear on page 3, the page number on page 4. The MW type="sig" and
type="pageNum" record what was on the page. The n= of PB and of
MILESTONE unit="sig" record an idealized, corrected, or expanded
version of the navigational information.

Hope this is at least interesting, if not helpful.

>  2. Page- and column-breaks
I have to go to bed now ... perhaps tommorrow.