Separate a missing name from missing data

NODATA does not create an NXDOMAIN cut.

• A resource record set (RRset) groups records of one type at a name. An empty non-terminal (ENT) is an existing name with no RRsets of its own but with descendants that have data. For example, leaf.branch.example. can have an A record while branch.example. itself has none. The intermediate branch still exists (§3.1; RFC 4592 §§2.2.2–2.2.3).
• For the selected ENT query, the correct result is NODATA: response code NOERROR (0) and an empty answer section. It is not NXDOMAIN. Here no alias is involved. NODATA is a description of the result, not a separate numeric DNS response code (§3.1).
• An ordinary existing host can likewise lack AAAA while having A records. A negative cache entry for missing data is scoped to name, requested type and class; an AAAA miss must not be turned into absence of the name or its A records (RFC 2308 §5, contrasted with RFC 8020 §3.2).
• Authoritative servers returning NXDOMAIN for an ENT are incorrect; RFC 8020 §5 explains how this can wrongly hide existing descendants and is incompatible with DNSSEC. The failed classification is stopped before creating a cut in this teaching scene. It is not a new RFC-mandated error response or a guarantee that every resolver repairs a bad answer.
• This publication clarifies RFC 1034’s distinction between nonexistent nodes and ENTs. It does not replace DNS lookup, wildcard synthesis, alias processing or all negative-caching rules. A timeout or SERVFAIL is not evidence for the NXDOMAIN cut described here (§§1,3.1,5).