Appendix A contains descriptions of subfields that are used to link field data to specific institutions or to other fields.  These subfields are defined for several ($0 and $5) or most ($6 and $8) fields in the format, thus their descriptions are brought together in this appendix.  The subfields are included in field level subfield lists wherever they are defined, with links to this appendix.

Specific subfield information:

$0  Authority record control number or standard number

$1  Real World Object URI

$5  Institution to which field applies  (NR)

$6  Linkage

$8  Field link and sequence number

Content designator history:

$0 - Authority record control number or standard number  [new, 2015]

$0 - Authority record control number or standard number  [redescribed, 2016]

In 2016, the requirement to precede a dereferenceable URI (such as an HTTP URI) in subfield $0 with the parenthetical prefix code "(uri)" was removed.

$1 - Real World Object URI [new, 2017]

$6 - Linkage [redescribed, 2018]

Scope of $6 broadened to allow for the recording of script identification codes taken from ISO 15924.

$8 - Field link and sequence number

a - Action  [new, 2004]

p - Metadata provenance  [new, 2012]

u - General linking, type unspecified  [new, 2016]

x - General sequencing  [new, 2004]

See also: