About Z39.50 Object Identifiers

Certain Z39.50 objects are registered so that they may be referenced unambiguously within ASN.1 definitions. This applies to objects of type OBJECT IDENTIFIER and EXTERNAL.

The Z39.50 ASN.1 descriptions (Z39.50 APDUs as well as descriptions within appendices) include various parameters of type OBJECT IDENTIFIER, for example, attributeSetId, diagnosticSetId, preferredRecordSyntax, ResourceReportId; and various parameters of type EXTERNAL, for example recordSyntax.

Thus for example, when an ASN.1 parameter 'attributeSetId' is of type OBJECT IDENTIFIER, when the ASN.1 structure is encoded for transmission it is to include an object identifier that identifies an attribute set, e.g. bib-1. When an ASN.1 parameter 'recordSyntax' is of type EXTERNAL, the encoded ASN.1 structure is to include an OBJECT IDENTIFIER (within the EXTERNAL structure) that identifies a record syntax.

In all cases the OBJECT IDENTIFIER must identify the object globally and unambiguously. So, it must be registered by some registration authority.

Method of Registration

Registration of an object is the assignment of an unambiguous identifier -- a leaf-node on the global registration tree. Non-leaf nodes of the tree correspond to registration authorities. At the top of the hierarchy are first-level registration authorities, including ISO. Directly under ISO, at level 2, is a node called "member-body". Under that node is a node for ANSI. The registered object identifier for ANSI is represented symbolically as: {iso member-body ANSI}. It is represented numerically as: 1.2.840 (1 for ISO, 2 for "member-body" and 840 for ANSI).

ANSI is thus the registration authority for all object identifiers with prefix 1.2.840. ANSI has assigned a node for Z39.50 directly subordinate to the ANSI node. The registered object identifier for the Z39.50 standard is:


This is the root of the Z39.50 object identifier tree. The Z39.50 Maintenance Agency is thus the registration authority for all object identifiers with prefix 1.2.840.10003.

Z39.50 Object Classes

Immediately subordinate to the Z39.50 object identifier are the following object classes:
  1. application context definition
  2. abstract syntax for APDUs
  3. attribute set definition
  4. diagnostic set or diagnostic format
  5. abstract record syntax
  6. transfer syntax for non-bibliographic records
  7. resource report format
  8. access control format
  9. extended service definition
  10. user information format
  11. element specification format
  12. variant set definition
  13. schema definition
  14. tag set definition

These values are defined within the Z39.50 standard (Appendix OID). Objects in these categories are registered subordinate to their respective node,

For example:
The object identifier for the class "attribute set definition" is 1.2.840.1003.3. The attribute set bib-1 is assigned a value of 1, and so its object identifier is 1.2.840.1003.3.1

Several Z39.50 objects are defined within the Z39.50 standard. However, not all objects to be registered subordinate to a standard need be defined within the standard; they may be registered by act of the registration authority for that standard according to the procedures established by that authority. Z39.50 objects not listed in the standard are registered under their respective classes by the Z39.50 Maintenance Agency or by an organization to whom the maintenance agency delegates authority to register objects.

Local Object Identifiers

The Z39.50 Maintenance Agency delegates to registered implementors the authority to register local (as well as experimental) object identifiers, according to the procedures described in OID.6 and OID.7.
Library of Congress
April 9, 1998