anchor.diff:  Map<@RegExp(...) String, @RetailOrder Order> orders;
   ----
   
  -This would validate the map's key's against `@RegExp`, the map's values against `@RetailOrder` and apply cascaded validation of the map (values).
  +This would validate the map's keys against `@RegExp`, the map's values against `@RetailOrder` and apply cascaded validation of the map values (as well as the map object itself).
   
   * When selecting extractors, type parameters must be throroughly traced in the hierarchy. Consider this case where the order of the type parameters of `Map` is swapped in a sub-type:
   
  
positive.code: 
  * arrays of objects and all primitive data types
  * `java.util.Iterable` (when `@Valid` is given on the iterable element itself, the element and all its entries will be validated; this is to grant backwards compatability with BV 1.1; when `@Valid` is given on the type parameter of an iterable element, all the entries will be validated). A node of type `TYPE_PARAMETER` and with the name "<collection element>" will be added to the path when validating a type parameter constraint.
  * `java.util.Map` (when `@Valid` is given on the map element itself, the element and all its values will be validated; this is to grant backwards compatability with BV 1.1; when `@Valid` is given on the key type parameter, only the keys will be validated; when `@Valid` is given on the value type parameter, only the value will be validated. A node of type `TYPE_PARAMETER` and with the name "<map value>" will be added to the path when validating a type parameter constraint on the map value. A node of type `TYPE_PARAMETER` and with the name "<map key>" will be added to the path when validating a type parameter constraint on the map key.
  TODO: format of key representations
  * `java.util.Optional`. No node will be appended to the path when validating type-level constraints on `Optional`. Constraints given on an element of type `Optional` apply to the wrapped value by default (see below).
  * `javafx.beans.observable.ObservableValue`. No node will be appended to the path when validating type-level constraints on `ObservableValue`. Constraints given on an element of type `ObservableValue` apply to the wrapped value by default (see below).
  
negative.code: 
  * Invoke the new method `Configuration#addValueExtractor(ValueExtractor<?>)` (to apply it on the validation factory level)
  * Invoke the new method `ValidatorContext#addValueExtractor(ValueExtractor<?>)` (to apply it for a single `Validator`)
  * Specify the fully qualified class name of one or several extractors in `META-INF/validation.xml`: 
  
  [source,xml]
  ----
  