Dir-spec dir-source fields optional?

Hi Nick. Quick question, the 'dir-source' line of network status documents is defined as...

"dir-source" SP nickname SP identity SP address SP IP SP dirport SP orport NL

The identity, IP, dirport, and orport all have obvious constraints on their values but the nickname and address don't. I'm assuming that any string excluding spaces and newlines are fine.

I assume that none of these fields are optional so can either of these be an empty string? It would make my life a little easier if they can't (due to how keywords/values are split - v3 documents are a little different from other descriptor types in that respect and I've been ignoring it).

Thanks! -Damian

PS. I've been assuming that anything saying "IP address" means "IPv4 address" unless specified otherwise. I know that we're trying to branch out to add IPv6 support, but I doubt that was the intention when these specs were first written and by that reason IPv8 or whatever the future holds would also be perfectly valid.

If this is wrong and "IP address" means something other than "IPv4" then let me know. :)

PPS. Bonus points if these questions are answered via a spec patch!