Add photos: meta data file format

Hello,

The add photos form has an option to upload meta data files, but I am completely unable to find any documentation on the format for the meta data. Does anyone know, please? Also, is it possible to specify meta data when adding photos by URL?

Thanks in advance for any advice,

Grotius

The following information is required to get an answer:
Get this information from the PHP diagnostic (in the configuration wizard).
Gallery URL (optional but very useful):
Gallery version: 1.5.1
Apache version: 1.3.33
PHP version (don't just say PHP 4, please): 4.3.10
Graphics Toolkit: ImageMagick
Operating system: Debian GNU/Linux
Web browser/version (if applicable):