Where should I store film and developer metadata?

I develop my B&W photos which I scan. I would like to record the film I used and the developer in the image somewhere and I was wondering if there was a well defined place?

I looked up the exif spec and there don't seem to be tags for film or developer used. I am thinking of using keywords, but I won't be able to include detailed developing steps that way. I could use one of the comment fields.

What I've done is dump the exif content of my Nikon d80 and looked at the tags there. There are two or three that can be pushed into service to store the info you want.
I'll look them up tonight in my computer and let you know which they are.
I use exiftools in a batch workflow to set that info in my scanned files.

Here is an example of the file I use, delimited by html tags:

<film.txt>
-P
-overwrite_original
-CreateDate=2008:09:10 00:00:00
-FilmType=Astia 100F, 120
-ISO=100
-Make=ARAX
-Model=60 MLU
-Description=2008-09 7-Astia 6X6, standard E6
-Converter=Coolscan 9000 ED @4000
-XResolution=300
-YResolution=300
-LensModel=CZJena Flektogon 50/4, CZJena Sonnar 180/2.8
-Author=Nuno Pinto do Souto
-Copyright=Copyright:Nuno Pinto do Souto, 2008
</film.txt>

This is kept in the top level folder for that particular roll of film. One level down are all the jpgs I've made out of the original scanned tiff output,
which in turn is kept another level down.

To apply the exif info to the scanned tiffs, I run:
exiftool -@ ..\..\Film.txt *.tif
on the corresponding folder in a command line window.

And that's pretty much it.
HTH

Thanks, that was helpful. I'll probably do something similar to what you are doing. The pointer to exiftool is really useful. I didn't find it when I last fiddled with this stuff a few years ago, and I ended up hacking something of my own to read and write keyword tags.