User attributes are used for actually storing information in the directory, as opposed to OperationalAttribute which are used for storing state information used for internal server processing.
Whenever a SearchRequest does not contain any specific attributes to be returned, then all user attributes in matching entries will be returned.
An explicit value of "*" (the asterisk) may also be included to explicitly include all user attributes.!! More Information There might be more information for this subject on one of the following: