[yang-doctors] 2 yang beginner questions

[Toerless Eckert <[e-mail]>]

a) Is there some yang-users mailing list where i wouldn't have to bother
   yang-doctors precious time with beginner questions, but rather seek
   help from folks who may like me just be learning up yang themselves 
   (and be a bit ahead) ?

   Typically the most easiest way to learn something is to be subscribed
   to a list where other beginners ask questions and get them answered too ;-)

b) https://tools.ietf.org/html/draft-ietf-anima-voucher-07

   I am confused about the best way to express an OR condition.

   container voucher {
      leaf expires-on {
         must "not(../nonce)"
      }
      leaf nonce {
         must "not(../expires-on)"
      }
   }

   What we do WANT to achieve is that you may have at least one of 
   the leaf expires-on or nonce. Having both is fine too (inclusive or).
   Just not having either is not permitted.

   Is this the correct syntax to do that ? Is that the preferred syntax to do this ?

Thanks
    Toerless