[
  ;; accounts

  { :db/id #db/id[:db.part/db]
    :db/ident :account/name
    :db/valueType :db.type/string
    :db/cardinality :db.cardinality/one
    :db/fulltext true
    :db/unique :db.unique/value
    :db/doc "An account's name"
    :db.install/_attribute :db.part/db}

  { :db/id #db/id[:db.part/db]
    :db/ident :account/balance
    :db/cardinality :db.cardinality/one
    :db/valueType :db.type/bigdec
    :db/doc "The accounts balance"
    :db.install/_attribute :db.part/db}

  { :db/id #db/id[:db.part/db]
    :db/ident :account/min-balance
    :db/cardinality :db.cardinality/one
    :db/valueType :db.type/bigdec
    :db/doc "The accounts maximum balance"
    :db.install/_attribute :db.part/db}

  { :db/id #db/id[:db.part/db]
    :db/ident :ot/amount
    :db/valueType :db.type/bigdec
    :db/cardinality :db.cardinality/one
    :db/doc "Amount transacted"
    :db.install/_attribute :db.part/db}

  { :db/id #db/id[:db.part/db]
    :db/ident :ot/from
    :db/valueType :db.type/ref
    :db/cardinality :db.cardinality/one
    :db/doc "Transferee"
    :db.install/_attribute :db.part/db}

  { :db/id #db/id[:db.part/db]
    :db/ident :ot/to
    :db/valueType :db.type/ref
    :db/cardinality :db.cardinality/one
    :db/doc "Recipient"
    :db.install/_attribute :db.part/db}

  { :db/id #db/id [:db.part/user]
    :db/ident :credit
    :db/fn #db/fn { :lang "clojure"
                    :params [db id amount]
                    :code "(let [ e (datomic.api/entity db id)
                                  min-balance (:account/min-balance e 0)
                                  balance (+ (:account/balance e 0) amount) ]
                                  (if (>= balance min-balance)
                                    [[:db/add id :account/balance balance ]]
                                    (throw (Exception.  \"Insufficient funds\"))))" }}

  { :db/id #db/id [:db.part/user]
    :db/ident :transfer
    :db/fn #db/fn { :lang "clojure"
                    :params [db from to amount]
                    :code "[[:credit from (- amount)]
                            [:credit to amount]]"}}

 ]