Is it an error in AD LDAP database if an employee registered twice: as PersonClass and as PersonClass+UserClass

Question

Browsing an AD LDAP Database, I noticed that some employees registered twice: once as objectClass=Person, and another one as objectClass=Persond and objectClass=User.

In other words, two records in the AD LDAP database belong to one employee, or one employee has different distinguished names, so that the search on this person gives two results.

How it could happen? Is it an error in our database?

Answer 1

Directory servers that follow the directory information model have no restrictions on whether an attribute can appear twice in the database. Distinguished Names, however, must be unique. Some directory servers have a notion of attribute uniqueness, which, if enabled, would enforce the uniqueness of certain configured attributes, meaning that when such enforcement is configured, for example, for the attribute employeeNumber, the following could not occur (in the same database):

employeeNumber=0,o=organization1,dc=company,dc=com

and

employeeNumber=0,o=organization2,dc=company,dc=com

The above is a clumsy attempt to make an employee a member of two organizations. If uniqueness of the employeeNumber attribute (which in this case is a component of the distinguished name) is not enforced, then the above DNs become possible, though hardly advisable since better methods exist to establish membership of organizations.

There is nothing to prevent employees from being stored twice in your database, and this is a common occurrence and depends entirely on the data model used by the organization.