anchor.diff:  ;;   at: [:event/search :search/url] predicate: string?
   ----
   
  +Let's take a moment to examine the explain error output on that final example. There were two different kinds of failures detected. The first failure is due to the missing required `:event/timestamp` key in the event. The second is from the invalid `:search/url` value (a number instead of a string). We see the same parts as prior explain errors:
  +
  +* in - the path within the data to the failing value. This is omitted on the first error as it's at the root value but is the key in the map on the second error.
  +* val - the failing value, either the full map or the individual key in the map
  +* spec - the actual spec that failed
  +* at - the path in the spec where the failing value occurred
  +* predicate - the actual predicate that failed
  +
   The `multi-spec` approach allows us to create an *open* system for spec validation, just like multimethods and protocols. New event types can be added later by just extending the `event-type` multimethod.
   
   == Collections
  
positive.code: ;; val: :foo fails spec: ::name-or-id at: [:id] predicate: int?
  ----
  
  The explain output identifies the problematic value and the predicate it was evaluating. In the last example we see that when there are alternatives, errors across all of the alternatives will be printed.
  
  In addition to `explain`, you can use http://clojure.github.io/clojure/branch-master/clojure.spec-api.html#clojure.spec/explain-str[`explain-str`] to receive the error messages as a string or  http://clojure.github.io/clojure/branch-master/clojure.spec-api.html#clojure.spec/explain-data[`explain-data`] to receive the errors in a more extensive data format.
  
  [source,clojure]
  ----
  
negative.code: 
  [NOTE]
  ====
  This result also demonstrates the new namespace map literal syntax added in 1.9.0-alpha8. Maps may be prefixed with #: or #:: (for 0autoresolve) to specify a default namespace for all keys in the map. In this example, this is equivalent to `{:clojure.spec/problems ...}`
  ====
  
  == Entity Maps
  