Subfield $8 contains data that identifies linked fields and may propose a sequence for the linked fields.  Subfield $8 may be repeated to link a field to more than one other group of fields.  The structure and syntax for the field link and sequence number subfield is:

[linking number].[sequence number]\[field link type]

The linking number is the first data element in the subfield and required if the subfield is used.  It is a variable-length whole number that occurs in subfield $8 in all fields that are to be linked.  Fields with the same linking number are considered linked.

The sequence number is separated from the linking number by a period ( . ) and is optional.  It is a variable-length whole number that may be used to indicate the relative order for display of the linked fields (lower sequence numbers displaying before higher ones).  If it is used it must occur in all $8 subfields containing the same linking number.


084  0#  $alcc  [Library of Congress Classification]

153  ##  $aHE394.A$cHE394.Z$hTransportation and communications$hWater transportation$hWaterways$hBy region or country$hUnited States$jRiver improvement. By name of river, A-Z

763  08  $iUnder each:

763  10  $81.1$a.x$jPeriodicals. Serials$p153

763  10  $81.2$a.x3$jGeneral works$p153

763  10  $81.3$a.x4$jGeneral special$p153

The field link type is separated from preceding data by a reverse slash ( \ ).  It is a code indicating the reason for the link and it follows the link number, or sequence number if present.  In the absence of a field link type, it is assumed that subfield $8 is used for linking and sequencing related 6XX (Notes) or 76X (Number Building instructions and subarrangements) fields.  The use of subfield $8 to maintain the order of these fields is essential to the understanding and application of the subarrangement or table.  The following one-character field link type codes have been defined for use in subfield $8:

p - Metadata provenance

Code p is used in a record to link a field with another field containing information about provenance of the metadata recorded in the linked field.

u - General linking, type unspecified

Code u is used in cases when a specific link type is not appropriate.  Code u may serve as a default value when there is no information about the reason for the link available.

See also:

Appendix A:  Control Subfields