This topic presents the object classes that are defined in the standards. Object classes are groups of directory entries that share certain characteristics. The object classes are arranged into a lattice, based on the object class DS_O_TOP. In a lattice, each element, except a leaf, has one or more immediate subordinates but also has one or more immediate superiors. This contrasts with a tree, where each element has exactly one immediate superior. Object classes closer to DS_O_TOP are called superclasses, and those further away are called subclasses. This relationship is not connected to any other such relationship in this guide.
Each directory entry belongs to an object class, and to all the superclasses of that object class. Each entry has an attribute named DS_A_OBJECT_CLASS, which was discussed in the previous topic, and which identifies the object classes to which the entry belongs. The values of this attribute are object identifiers, which are represented in the interface by constants with the same name as the object class, prefixed by DS_O_.
Associated with each object class are zero or more mandatory and zero or more optional attributes. Each directory entry must contain all the mandatory attributes and can (but need not) contain the optional attributes associated with the object class and its superclasses.
The object classes defined in the standards are shown in the following table, together with their object identifiers.
Note: The third and fourth columns of the following table contain the contents octets of the BER encoding of the object identifier. All these object identifiers stem from the root {joint-iso-ccitt(2) ds(5) objectClass(6)}.
Object Identifiers for Selected Object Classes
| Object Identifier BER |
| Package | Attribute Type | Decimal | Hexadecimal |
| BDCP | DS_O_ALIAS | 85, 6, 1 | \x55\x06\x01 |
| BDCP | DS_O_APPLIC_ENTITY | 85, 6, 12 | \x55\x06\x0C |
| BDCP | DS_O_APPLIC_PROCESS | 85, 6, 11 | \x55\x06\x0B |
| BDCP | DS_O_COUNTRY | 85, 6, 2 | \x55\x06\x02 |
| BDCP | DS_O_DEVICE | 85, 6, 14 | \x55\x06\x0E |
| BDCP | DS_O_DSA | 85, 6, 13 | \x55\x06\x0D |
| BDCP | DS_O_GROUP_OF_NAMES | 85, 6, 9 | \x55\x06\x09 |
| BDCP | DS_O_LOCALITY | 85, 6, 3 | \x55\x06\x03 |
| BDCP | DS_O_ORG | 85, 6, 4 | \x55\x06\x04 |
| BDCP | DS_O_ORG_PERSON | 85, 6, 7 | \x55\x06\x07 |
| BDCP | DS_O_ORG_ROLE | 85, 6, 8 | \x55\x06\x08 |
| BDCP | DS_O_ORG_UNIT | 85, 6, 5 | \x55\x06\x05 |
| BDCP | DS_O_PERSON | 85, 6, 6 | \x55\x06\x06 |
| BDCP | DS_O_RESIDENTIAL_ PERSON |
85, 6, 10 | \x55\x06\x0A |
| BDCP | DS_O_TOP | 85, 6, 0 | \x55\x06\x00 |