[xml] parsing using SAX

[Adrian Feiguin <feiguin magnet fsu edu>]

Hi! I need some help with the following situation: My document model in 
SciGraphica has the following structure:
<project>
 <worksheet>
 ...
 </worksheet>
 <plot type="2d">
 ...
 </plot>
 <plot type="3d">
 ...
 </plot>
</project>

The idea is that each plot type is a plugin, with its own SAXHandler to
parse xml files. So I need the SAXHandler for the project to call the
SAXHandlers of the plugins at each <plot> node to parse each chunk between
<plot> and </plot>, and then come back to parse the rest of the tree. 

To be more specific, in the startElement callback for the project, I find
that my plot is of type "2d". Then I need to call the function to parse
that chunk, the 2d plot with it's own sub-tree, using its own SAXHandler,
and  its own startElement callback, and then come back to parse the rest.

I hope I've been clear, I'd appreciate any help. Thanks a lot!
<ADRIAN>