Yes, I think if we can convince ourselves that there won't be that many different possibilities for representing a vector, then a simple boolean might unify everything. This approach doesn't 'scale' but I don't know there are other representations we must have.
The issue of named vectors is interesting. There's not really such a thing as an optional field in Hadoop serialization. You can fake it with a boolean but that starts to be messy. Messy might be necessary as vectors perhaps take on more metadata -- though I can't envision much more. So perhaps it is right and proper to retain a second serialization format, in NamedVectorWritable, which is really the "vector with metadata" serializer versus VectorWritable's "pure vector" serializer. It has a logic to me. It gets rid of writing the class name which is indeed unpalatable. Thoughts before I go tearing through again?
