Inside the .oo3 bundle, and once unzipped (if necessary), the OO file is simply an XML text file, with a structure defined by:

http://www.omnigroup.com/namespace/O...outline-v3.dtd

I'm not quite clear what you are doing, and I don't know what sort of processing speed you need, but my first thought would be to get someone to write you an XSLT template to transform the OO XML into whatever it is that you need.