Adding information to graphs

[Thom Burnett <Thom.Burnett@cognigencorp.com>]

Does S-Plus (or R) have any provisions for adding informationation to 
graphs it creates?
PNGs contain in the header places for metadata like the date of 
creation, author, source of data, etc.
How can I add that data when creating a PNG?
Are there any libraries that include that feature?

I've just started looking into this topic so any information, however 
basic, would help.