Om Nex Foreign Keys

{:users
 [[:user/by-id 1] [:user/by-id 3] [:user/by-id 4] [:user/by-id 6]],
 :roles [[:role/by-id 1]],
 :user/by-id
 {1
  {:id 1,
   :email "foo@example.com",
   :role 1},
  3
  {:id 3,
   :email "bar@floyhamilton.nl",
   :role 1},
  4
  {:id 4,
   :email "baz@example.com",
   :role 1},
  6
  {:id 6,
   :email "nom@example.com",
   :role 1}},
 :role/by-id {1 {:id 1, :name "admin"}}}

(defui Role
  static om/Ident
  (ident [this {:keys [id]}]
         [:role/by-id id])
  static om/IQuery
  (query [this]
         [:id :name]))

(defui User
  static om/Ident
  (ident [this {:keys [id]}]
         [:user/by-id id])
  static om/IQuery
  (query [this]
         '[:id :email :role [:role/by-id ~role]]))