Functional database - chapter 

I have a couple of questions about this:

a) We actually used `with-meta` before this, in `make-attr`. If we're going to talk about this, I think it we should do it at first usage?

b) How are you determining what to treat as meta, and what to make first-class on the data structure? The reason I ask is that if we omitted using meta at all, this section could be merged into the previous with just a couple of lines of explication (explaining that `from-eav` and `to-eav` are used to convert to-and-from the canonical datom ordering.)