[Zope] Files, and their whereabouts

Greetings, I am currently modifying the Image object (patch to follow soon), and found something confusing. What is the difference between files in the lib/python/App directory, and those in the lib/python/OFS ? Obviously their content, but what is the intended function of files in each directory? From what i saw on the App directory, it looked to be the image object. But when my changes didn't take effect, an rgrep showed that what i wanted to mess with was in OFS. I've not done a lot of hacking about with ZOPE source before, so please excuse my ignorance if what I'm asking should be clear. (o8 -- Have a better one, Curtis. <dtml-var standard_work_disclaimer>