Which EXIF tag to store keyword/tag for a photo?

Question

I am developing a photo gallery which will read/write EXIF tags. I will put photo title in the EXIF tag DocumentName and description in EXIF tag ImageDescription. I also plan to use the geo-tags. But what about photo tags/categories? I want to store a space-separated string of the tags a photo is tagged with in my system. Is there any EXIF tag that is normally used for this type of information? I could write my own (i.e. PhotoTags) but I guess that is not really of any use except for internally in my system (where this information is stored in a database anyway).

Answer 1

I think that will want to look into IPTC and/or XMP (not entirely clear over their relation) for storing metadata about images (such as keywords/tags, title, description and so on).

Answer 2

There's no EXIF tag for this, but there is an IPTC "keywords" tag. JPEG can handle IPTC records, so there should be no problem.