  #### The `required`, `allow_none`, `allow_blank` and `default` arguments.
  
  REST framework now has more explict and clear control over validating empty values for fields.
  
  Previously the meaning of the `required=False` keyword argument was underspecified. In practice it's use meant that a field could either be not included in the input, or it could be included, but be `None`.
  
  We now have a better seperation, with seperate `required` and `allow_none` arguments.
  
  The following set of arguments are used to control validation of empty values:
  
 
</s> remove We now have a better seperation, with seperate `required` and `allow_none` arguments.
 </s> add We now have a better separation, with separate `required` and `allow_none` arguments. </s> remove * Some data, such as many-to-many relationships, cannot be added to the object instance until after it has been saved. This type of data needed to be hidden in some undocumentated state on the object instance, or kept as state on the serializer instance so that it could be used when `.save()` is called.
 </s> add * Some data, such as many-to-many relationships, cannot be added to the object instance until after it has been saved. This type of data needed to be hidden in some undocumented state on the object instance, or kept as state on the serializer instance so that it could be used when `.save()` is called. </s> remove You can also still use the `many=True` argument to serializer classes. It's worth noting that `many=True` argument transparently creates a `ListSerializer` instance, allowing the validation logic for list and non-list data to be cleanly seperated in the REST framework codebase. 
 </s> add You can also still use the `many=True` argument to serializer classes. It's worth noting that `many=True` argument transparently creates a `ListSerializer` instance, allowing the validation logic for list and non-list data to be cleanly separated in the REST framework codebase.  </s> remove * `WriteableField` as the base class for read-write fields.
 </s> add * `WritableField` as the base class for read-write fields. </s> remove The `.restore_object()` method is now replaced with two seperate methods, `.create()` and `.update()`.
 </s> add The `.restore_object()` method is now replaced with two separate methods, `.create()` and `.update()`.
Previously the meaning of the `required=False` keyword argument was underspecified. In practice its use meant that a field could either be not included in the input, or it could be included, but be `None`.
  #### The `required`, `allow_none`, `allow_blank` and `default` arguments.
  
  REST framework now has more explict and clear control over validating empty values for fields.
  
Previously the meaning of the `required=False` keyword argument was underspecified. In practice its use meant that a field could either be not included in the input, or it could be included, but be `None`.
  
  We now have a better seperation, with seperate `required` and `allow_none` arguments.
  
  The following set of arguments are used to control validation of empty values:
  
keep keep keep keep replace keep keep keep keep keep
 Minor: fix spelling and grammar, mostly in 3.0 announcement 
docs/topics/3.0-announcement.md