Clojurians Log v2

Hello, is there a specification for what to expect in a call to the read function you supply to om.next?

The key parameter is either a property to look up, or the first element in an ident (not sure why on this)

env/query - the right hand side of a join, or nil?

env/query-root ~ :om.next/root or an ident?

etc etc

I am going by reading Tony Kay's tutorial plus plugging different queries into a heavily logging read, is there a more formal way to approach it?