Having model:

typedef uri {
  type string;
}
typedef specialized-uri {
  type uri;
}

container data {
  leaf value {
    type uri;
  }
}

Will result in following class hierarchy for typedefs:

SpecializedUri extends Uri

Container data will have builder with setValue(Uri value) method, which can accept also SpecializedUri,
but when serializing / deserializing data - this information that originally SpecializedUri was used is lost and returned value is only of type Uri.