XSL FO and the generation of "change bars"

Gentlepeople,

I have diligently searched the XSL FAQ and the XSL-List archives, as well 
as generally around the Web, without finding anything (at least not 
anything helpful) related to this subject. If I have missed a relevant bit 
of information, I will be grateful for somebody to point me to it.  It was 
suggested to me by a reader of a message that I posted on the XSL-List that 
perhaps the www-xsl-fo list participants might have a clearer view of the 
situation and thus might offer more helpful responses.

Many text publishing products (e.g., LaTex, DECdocument, Microsoft Word, 
Adobe Framemaker) have the ability to apply so-called change bars (those 
vertical rules alongside one edge of portions of a document) to indicate 
new or changed bits of text in a document, as well as other marks (e.g., a 
bullet) to indicate deleted material.

As some of you may know, I am responsible for producing a series of 
documents (the ISO SQL standard) that is frequently updated and distributed 
to a largish group of people for on-going development work.  Change bars 
are essential to allow participants to readily see what has changed amongst 
about 2,000 pages of text.  I am currently producing these documents using 
DECdocument, but am in the process of converting them to XML, producing PDF 
via XSL FO (using RenderX's XEP product).

I do not immediately see how to implement change bars through XSLT and XSL 
FO.  Of course, I am capable of defining (in a DTD or Schema) tags/elements 
such as "Start a changebar section" and "End the current changebar 
section", as well as "At this point, indicate that something was deleted", 
and I am happy to place such tags/elements at the appropriate places in my 
XML files as I edit them.  I am even reasonably confident of my ability to 
write XSLT to create XSL FO appropriately.  The problem is, of course, 
getting those tags/elements to result in change bars alongside the margins 
of the page.

If there is some obvious way, then please tell me and I'll be suitable 
embarrassed.  If there is some non-obvious way, then I will be very pleased 
to learn how to accomplish this. If there is no known way, then I'll be 
disappointed ;^)

One suggestion that I am investigating is the possibility of "activating" 
the borders alongside <fo:block> sections corresponding to paragraphs 
(etc.) of material that is surrounded by those tags/elements that I'm 
willing to define and use.  However, that approach has the disadvantage 
that the "change bar" is not necessarily at a specific distance from the 
edge of the "paper" (when this is rendered into, say, PDF), but at a 
specific distance from the text...which may be indented varying amounts in 
different <fo:block>s.

Many thanks for all relevant responses!
    Jim
========================================================================
Jim Melton --- Editor of ISO/IEC 9075-* (SQL)     Phone: +1.801.942.0144
Oracle Corporation            Oracle Email: mailto:jim.melton@oracle.com
1930 Viscounti Drive          Standards email: mailto:jim.melton@acm.org
Sandy, UT 84093-1063           Personal email: mailto:jim.melton@acm.org
USA                                                Fax : +1.801.942.3345
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=  Facts are facts.  However, any opinions expressed are the opinions  =
=  only of myself and may or may not reflect the opinions of anybody   =
=  else with whom I may or may not have discussed the issues at hand.  =
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Received on Thursday, 10 May 2001 02:27:06 UTC