"invalid structural object class chain"

Dear wise guys!

Sorry for a "newby" question: I would like to load following LDIF:

dn: cn=Zaphod Beblebrox, ou=people,cu=user,cu=a-d,cu=natco,dc=cax,dc=airbus,dc=com cn: Zaphod Beblebrox objectClass:Top objectClass: Person objectClass: organizationalPerson objectClass: inetOrgPerson objectClass: account objectClass: posixAccount gidNumber: 42 homeDirectory: /home/ZZ-Plural-Z-Alpha userid:zaphod

I get back: ldapadd: Object class violation (65) additional info: invalid structural object class chain (inetOrgPerson/account)

I searched before I wrote this mal the Web/ the Forum / the FAQ / the admin-Guide :-) I found at the admin guide chapter C1.13 an description about this issue. BUT: I´m sorry! I don´t understand this real hard to read english.

All what I hopfully know is, that a subsequent class of a Structural can be one or more auxiliary OR an other Structural. I assume that Top->Person->organizationalPerson->inetOrgperson "looks" like one structural class in case that they inherit via the SUP keyword ( called superclass ?? ) For that I do not understand why the account object class can´t be "connect" to that superclass. What´s wrong here and how do can I use the account as subsequent class of inetOrgPerson. The "connect" of posixAccount to account should be also possible.

Thanks a lot for your help in advance,

Karsten (Alien)