2004.10.04 15:53 "Re: [Tiff] IPTC tags", by Bob Friesenhahn
Metadata is good.
Metadata is mighty vague, and would equally well cover a handfull of other tags. A small list of most common/usefull fields remains desirable as a more helpfull tag description.
There is a published standard for the IPTC Newsphoto metadata format. It is worth mentioning that the IPTC Newsphoto metadata format is officially defunct (according to the IPTC organization). Regardless, it continues to be strongly supported by application software.
Metadata is indeed mighty vague. With EXIF, IPTC NewsPhoto, XMP, and "Photoshop" tags often occuring in the same file, there is a huge amount of redundancy. Many/most fields are optional.