6.2. Protobuf Encoding

package book_sample;  
message Book {      
      required string title = 1;
      required string description = 2;
      required int32 publicationYear = 3; // no native Date type available in Protobuf
      
      repeated Author authors = 4;
}
message Author {
    required string name = 1;
    required string surname = 2;
}