What if its a 2025 car or tv? Then it is both. Your tag will need a whole new ontology.
Thinking about it though, you're the best person I know for that challenge!
Discussion
Any tag is an array. We can just add fields onto the array, like we do with `m` and `M` and `r` and etc. tags.
It's a classification system, yes, but otherwise you can't have a generic ratings app, where you can just search for topics and see lists like Top Ten Books, Favorite Cars, Best Spreadsheet Apps.
For a classification system, schema.org is used and maintained, so maybe a flat representation of that gives you a starting point.
The ‘o’ could start at the Thing level.
nostr:nprofile1qyw8wumn8ghj7argv43kjarpv3jkctnwdaehgu339e3k7mf0qy2hwumn8ghj7un9d3shjtnyv9kh2uewd9hj7qgmwaehxw309a6xsetxdaex2um59ehx7um5wgcjucm0d5hsqgxufnggdntuukccx2klflw3yyfgnzqd93lzjk7tpe5ycqdvaemuqctmr050 nostr:nprofile1qyt8wumn8ghj7mn0wd68yetvd96x2uewdaexwtcprdmhxue69uhhg6r9vehhyetnwshxummnw3erztnrdakj7qg3waehxw309ahx7um5wgh8w6twv5hsqgrszgsjsfemmsr6lxl8wf06t39uplq5dpntasudgsmqm39udnqchyt6zfwh it includes medical