Appendix A contains descriptions of five subfields that are used to link field data to specific institutions or to other fields.  These subfields are defined for several ($w, $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:

$w  Bibliographic record control number

$0  Authority record control number or standard number

$5  Institution to which field applies

$6  Linkage

$8  Field link and sequence number

Content designator history:

$w - Bibliographic record control number  [new, 2007]

$0 - Authority record control number  [new, 2007]

$0 - Authority record control number  [redefined, 2010]

$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.

$0 - Authority record control number or standard number  [redescribed, 2017]:  In 2017, the scope of subfield $0 was broadened to include classification record control number.

$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:

Appendices