Unfortunately I think the documentation you seek is largely unavailable. :( This isn't on purpose, it just hasn't been done yet. Let me see if I can answer some of the questions here, but I'm going to CC the Devel list which can probably help also.
On Fri, 2007-07-27 at 08:54 -0500, Kent Tenney wrote:
I haven't yet found;
- an explanation of the xml in the .inx file
There is some information in the Wiki on this. I've started an XML Scheme (attached) but it is not complete and I'm not sure it even validates (my first XML Schema). If you have specific questions I'd be happy to answer them.
- the api available to Python scripts
The scripts themselves aren't locked into any API. The data comes through command line parameters and STDIN/STDOUT to the script. There is a convenience library in the extensions directory which provides come common functionality. If you have questions on those functions, please ask on -devel.
- a discussion of how Inkscape processes the share/extensions dir
I'm not sure what you're looking for here. Sorry. Could you please reask this a different way?
--Ted