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