Mmmm not sure about the difference ?

From http://cstheory.stackexchange.com/questions/3842/whats-the-difference-between-online-and-incremental-optimization it seems that we need online here since we could be receiving examples in a stream at uncertain times and from uncertain sources. Indeed, during the streaming of the reuters data we don't control which files get read first and among the '0' class we can have really different documents.