Why do some parent NSs "lie" about delegation records?

[Stephane Bortzmeyer]

On Wed, Jan 07, 2004 at 07:06:47AM -0600,
 Len Conrad <LConrad at Go2France.com> wrote 
 a message of 60 lines which said:

> An "honest" parent:
> 
> dig @a.gtld-servers.net yahoo.com ns

Broken Atlas.
 
> In contrast, a "lying" parent:
> 
> # dig @ns1.ausregistry.net. yahoo.com.au ns

Correct BIND 9.
 
> It appears the com.au. parent NS is "lying" about not having an
> ANSWER to 

No, it's right. (It is for the same reason that glue NS are not signed
in DNSsec.)

For another example:

dig @nsX.nic.fr NS yahoo.fr 

X == 1 : BIND 8
X == 2 : nsd
X == 3 : BIND 9