README_V3.md in schemacop-3.0.0.rc3 vs README_V3.md in schemacop-3.0.0.rc4

@@ -88,11 +88,11 @@
   information why the validation failed.
 
   Example:
 
   ```ruby
-  Schemacop::Schema3.new do
+  Schemacop::Schema3.new :hash do
     int!
   end
 
   # => Schemacop::Exceptions::InvalidSchemaError: Child nodes must have a name.
   ```
@@ -378,11 +378,11 @@
 ```
 
 ### Array
 
 Type: `:array`\
-DSL: `arr`
+DSL: `ary`
 
 The array type represents a ruby `Array`.
 It consists of one or multiple values, which can be validated using arbitrary nodes.
 
 #### Options
@@ -585,12 +585,13 @@
 
 #### Options
 
 * `additional_properties`
   This option specifies whether additional, unspecified properties are allowed
-  (`true`) or not (`false`). By default, this is `true` if no properties are
-  specified and `false` if you have specified at least one property.
+  (`true`) or not (`false`). By default, this is `false`, i.e. you need to
+  explicitly set it to `true` if you want to allow arbitrary additional properties,
+  or use the `add` DSL method (see below) to specify additional properties.
 
 * `property_names`
   This option allows to specify a regexp pattern (as string) which validates the
   keys of any properties that are not specified in the hash. This option only
   makes sense if `additional_properties` is enabled. See below for more information.
@@ -669,9 +670,64 @@
 schema = Schemacop::Schema3.new :hash do
   int! :foo
 end
 
 schema.validate!(foo: 42, 'foo' => 43) # => Schemacop::Exceptions::ValidationError: /: Has 1 ambiguous properties: [:foo].
+```
+
+In addition to the normal node options (which vary from type to type, check
+the respective nodes for details), properties also support the `as` option.
+
+With this, you can "rename" properties in the output:
+
+```ruby
+schema = Schemacop::Schema3.new :hash do
+  int! :foo, as: :bar
+end
+
+schema.validate!({foo: 42}) # => {"bar"=>42}
+```
+
+Please note that if you specify a node with the same property name multiple
+times, or use the `as` option to rename a node to the same name of another
+node, the last specified node will be used:
+
+```ruby
+schema = Schemacop::Schema3.new :hash do
+  int? :foo
+  str? :foo
+end
+
+schema.validate!({foo: 1})      # => Schemacop::Exceptions::ValidationError: /foo: Invalid type, expected "string".
+schema.validate!({foo: 'bar'})  # => {"foo"=>"bar"}
+```
+
+As well as:
+
+```ruby
+schema = Schemacop::Schema3.new :hash do
+  int? :foo
+  int? :bar, as: :foo
+end
+
+schema.validate!({foo: 1})          # => {"foo"=>1}
+schema.validate!({foo: 1, bar: 2})  # => {"foo"=>2}
+schema.validate!({bar: 2})          # => {"foo"=>2}
+```
+
+If you want to specify a node which may be one of multiple types, use the `one_of`
+node (see further down for more details):
+
+```ruby
+schema = Schemacop::Schema3.new :hash do
+  one_of! :foo do
+    int
+    str
+  end
+end
+
+schema.validate!({foo: 1})      # => {"foo"=>1}
+schema.validate!({foo: 'bar'})  # => {"foo"=>"bar"}
 ```
 
 ##### Pattern properties
 
 In addition to symbols, property keys can also be a regular expression. Here,