Liveness in a store is determined by reachability from the root object. (When garbage collection is implemented, dead objects will be collected on gc's.) The root object is a BTree which is like a hash-table with sorted keys. See Using BTrees.
You can put something into the root object by
* (add-to-root "my key" "my value") => NIL
and get things out via
* (get-from-root "my key") => "my value" => T
The root object is available as
* (controller-root *store-controller*) => #<BTREE {492AE37D}>
It is an instance of a class "btree"; See Using BTrees.