Organization identification schemes registered according to ISO/IEC 6523-2
Subsequent arcs are International Code Designators (ICDs) which are all integers from 1 to 9999. The ICD has no significance other than unique identification of an organization identification scheme.
An ICD value is allocated to an organization identification scheme in accordance with the procedure specified in ISO/IEC 6523-2. ICD values are assigned sequentially in the order in which entries are added to the register. An ICD value once assigned shall not be reallocated. When an organization identification scheme ceases to be supported, the registration entry shall be marked as such, but the entry itself shall be kept in the register, and the ICD value shall not be reallocated.
Interchanging partners may want, by prior agreement, to interchange organization identifiers allocated by an identification scheme to which an ICD value has been assigned, or for which the assignment of an ICD value is pending. The range of ICD values between 9900 and 9999 is reserved for that effect. The interchange partners shall agree on the identification of the identification scheme, using one of the above reserved values.
An organization may be identified by more than one identification method.