It looks like you've made author a required field, but NKBIP-01 says it's optional.
On the uploader, I have a construct_d_tag function with a fall-through statement, that adds on each additional available variable, ending with $dTagTitle . "-by-" . $dTagAuthor . "-v-" . $dTagVersion

So, something like The-fox-and-the-hound-by-Aesop-v-fourth-revised