Code Relationship

[I apologise if this has been discussed  via the teleconferences in the past...]In looking at the current draft spec, I was wondering if there would be supportfor defining the relationships between some of the codes.In particular, some common relationships like: "related-term", "broader-term", "narrower-term"I could not see this mentioned in the Requirements document either.
 Cheers...  Renato IannellaNICTA