* compare the ETag sent by the client and the generated one, break here if they do not match
* use [[PHP_Extensions#LDAP_Assertion_Control|LDAP Assertion Control]] when sending the edit request to the LDAP with the fetched <code>csn</code> as assertion
Notes:
* advantage over proposal II: this can easily be extended to the case where a resource consists of multiple LDAP objects by concatenating the different <code>csn</code> entries in a reproducible fashion
= Implementation proposal II =