Master index for modular docs

[Denis Bradford <denis.bradford@verizon.net>]

I'm converting an html-sourced help system to DocBook. The help is 
delivered in Eclipse, man pages, a web site, and PDF. So far no problem. 
Here's the problem: The HTML version currently has an index. How to 
generate a master index for a bunch of modularized documents?

The only approach I can think of is to wrap everything up in a set and 
build it to generates the setindex. Problem is it also generates all the 
modules. That seems to defeat one of the purposes of modularizing: not
having to build the whole shebang every time you change something.
Is there a way to avoid generating all the modules - or a better 
approach to indexing altogether?

P.S. I found a docbook-apps mail thread where Bob suggests a 
customization for generating just index.html (the front page, not the 
index component) while suppressing the component templates. ("Multi-part 
document, multiple stylesheets",
http://sourceware.org/ml/docbook-apps/2005-q1/msg00604.html)

I tried a similar thing with setindex, but failed. Perhaps I don't 
correctly understand the difference between suppressing the xsl 
processing of modules (which contain the index entry targets!) and 
suppressing just their HTML output.