keywords, categorizing and collections/sets

I'm working on my online image viewer and it seems to me that organizing images is the hard part.

Who uses a program like "Light Room" or "Bridge" to categorize images? How do you use it?

My goal is to take such encoded data and use it as an optional tool to manage the online images. Ie, to be able to use the existing keywording and other marking.

I'm just getting started on this, I imagine that this is encoded in the EXIF data along with camera settings, is that right?