Yeah I was thinking the former: kind B claims to inherit from kind A. It is real inheritance but requires manual work (asking clients to include new kinds)

How about a `k` tag that declares inheritance?

In my kind 32267 I could add ["k", 30818] so then wiki clients can query for { kinds: [30818] } and { "#k": [30818] } 

 difference with yours being that the supertype need not declare anything 

 Yeah, I like this. I actually think it’s better than what I suggested. Less rigid.