[4/5] Concept of broken catalog zones
The DNS catalog zones draft version 5 document describes various situations when a catalog zone must be considered as "broken" and not be processed.
BIND should implement those checks to be compatible with the draft.
As of version -05, these are the situations listed in the draft that a catalog zone is "broken"
The names of member zones are represented on the RDATA side (instead of as a part of owner names) of a PTR record, so that all valid domain names may be represented regardless of their length. This PTR record MUST be the only record in the PTR RRset with the same name. More than one record in the RRset denotes a broken catalog zone which MUST NOT be processed.
The CLASS field of every RR in a catalog zone MUST be IN (1).
All catalog zones MUST have a TXT RRset named version.$CATZ with exactly one RR. Catalog consumers MUST NOT apply catalog zone processing to zones without the expected value in the version.$CATZ TXT RR (in other words, such a catalog zone is "broken").
The coo property PTR RRset MUST consist of a single PTR record. More than one record in the RRset denotes a broken catalog zone which MUST NOT be processed.