= Overview =
The idea of the <code>ETag</code> is that one can edit/update resources without overwriting the changes made by somebody else.
Since the REST API may not be the only client to the LDAP server and the REST API can't protect itself from concurrent writes to the LDAP on the same objects (due to the PHP principles of request-based execution), the LDAP must therefore most likely be part of the solution for generating and validating ETags.
= Implementation proposal I =