Tags for scanned collection

[spockk]

Hello,

I'm organizing my archive of old scanned photos (tiffs & jpegs) with great help of exiftool and came to conclusion that i need to add some additional information to my files.
First group is let's say 'hardware' related: Camera, Paperscan/Filmscan, Film, Film type (slide/negative), Frame number
Second group is more 'generic': date taken, date scanned, software, author, people on picture, comments and so on.

After quick reading about XMP tags here at exiftool site and at http://www.exiv2.org/metadata.html i decided that i should use XMP tags only for my purposes:
1. I wouldn't want to add or modify existing EXIF tags because many of my files have a lot of EXIF tags filled in already, for instance, Make/Model fields are "Nikon Coolscan", "Epson" etc.
2. Because there are no proper fields in EXIF for my 'first group'.
3. Finally i think i should work with one kind of tags - EXIF fields are for scanners/digital cameras, XMP tags are for user and software.

And finally i feel completely lost in all these groups, namespaces and how they have to be properly be fiiled in.
With power of exiftool i can add even single tag from any, even custom namespace, but... How custom namespaces will be treated in future? And it seems that it will take a lot of time to be familiar with all of these things and to understand how to properly use them.
So I'm looking for advice. Probably my wishes have simple solutions and i'm just inventing a wheel.
Any suggestions are very welcome.

PS Excuses for my ugly English.

[Phil Harvey]

Yes, the possibilities with XMP are endless.  I suggest keeping to the namespaces defined in the XMP specification if possible (the underlined namespaces in the ExifTool XMP tags documentation).  But if you can't, the one advantage of XMP is that tags can be extracted with meaningful names even if they aren't pre-defined, which makes it future-proof to a certain degree.

- Phil