python-xmp-toolkit - Python XMP Toolkit - a python library for reading, writing and manipulating XMP metadata.
This appears to be the best tool to use for read/write with XMP in Python. by Apr 12
This gives a decent description of JPEG and how it store metadata. by Apr 12
This appears to be a descent tool for extracting metadata. My thought is that when users upload a image to the server, we utilize this library to parse the image data and translate it over to a xml file. The benefit being we can download tag information on lots of images in a single xml file versus searching through each image for a particular tag in each images raw data. by Apr 12