Library of Congress >> MARC >> Authority >> 7XX

7XX - Heading Linking Entries-General Information


MARC 21 Authority
October 2014

"Full" documentation refers to the MARC 21 Format for Authority Data that contains detailed descriptions of every data element, along with examples, input conventions and history sections.

"Concise" documentation refers to the MARC 21 Format for Authority Data that contains abridged descriptions of every data element, along with examples.


DEFINITION AND SCOPE

The 7XX Heading Linking Entry fields provide a machine link within a system between equivalent or hierarchical headings whether they are structured in the same or different form, are from the same or different authority files or printed thesauri, or whether they exist as separate authority records. The inclusion of a linking entry field in an established heading or established heading and subdivision record for a name, name/title, uniform title, topical term, form term, or extended subject heading or in an established heading record for an authorized subject subdivision may be used to relate such headings as:

7XX field tag identifies whether the heading linking entry field contains an established heading (fields 700-762) or an authorized subdivision heading (fields 780-785). The second indicator or the subfield $2 identify the authority system to which the heading in field 7XX belongs. Subfield $0 (Authority record control number or standard number) contains the system control number or standard number of the related record when a separate MARC authority record exists for the 7XX heading.

A relationship that cannot be adequately expressed by the 700-785 linking entry fields is described textually in field 788.


GUIDELINES FOR APPLYING CONTENT DESIGNATORS

Guidelines for the second indicator, subfield $2 (Source of heading or term), subfield $w (Control subfield), subfield $i (Relationship information), and subfield $4 (Relationship code) in the 7XX fields, as well as special instructions for field 788 are provided in this section. Guidelines for applying the other content designators defined for fields 700-785 are provided in the General Information sections for each corresponding field.

First indicator position and all of the subfield codes defined for field 788 (Complex Linking Entry Data) are described in the description of that field. The second indicator position is described in this section.

INDICATORS

Second Indicator - Thesaurus

Name and/or subject heading system or thesaurus used in constructing the heading.

0 - Library of Congress Subject Headings/Name authority file

Heading conforms to and is appropriate for use in the Library of Congress Subject Headings (LCSH) and/or the Name Authority Cooperative (NACO) file that are both cooperatively maintained at the Library of Congress.

1 - LC subject headings for children's literature

Heading conforms to the "AC Subject Headings" section of the LCSH.

2 - Medical Subject Headings/NLM name authority file

Heading conforms to Medical Subject Headings (MeSH) and/or the National Library of Medicine name authority files.

3 - National Agricultural Library subject authority file

Heading conforms to the U.S. National Agricultural Library subject authority file.

4 - Source not specified

Heading conforms to a controlled list that cannot be specified by another second indicator value or by an identifying MARC code in subfield $2.

5 - Canadian Subject Headings/LAC name authority file

Heading conforms to and is appropriate for use in the Canadian Subject Headings and/or the Library and Archives Canada name authority file.

6 - Répertoire de vedettes-matière

Heading conforms to and is appropriate for use in the Répertoire de vedettes-matière that is maintained by the Bibliothèque de l'Université de Laval.

7 - Source specified in subfield $2

Heading conforms to a controlled list other than that specified by one of the other defined values and for which an identifying MARC code is contained in subfield $2.

SUBFIELD CODES

$i - Relationship information

Subfield that records in textual form the designation of a relationship of the entity in a 7XX field to the 1XX entity in the record.

008/11 a
150 ##$aApples
750 #7$iBroader mapping$aFruit$4BM$2tgm
[The heading in 750 derived from the Thesaurus for Graphic Materials is broader than that of the 150 derived from LCSH.]

$w - Control subfield

Up to two character positions (designated by $w/0 or $w/1) that control the generation of a link display or indicate the complexity of a heading in a 700-785 field. Used only if the display is to be suppressed or the replacement of a heading should be reviewed.

Because the definitions of the codes in subfield $w are dependent on the character position in which they occur, the coding of any character position mandates that each preceding character position contains a code or a fill character (|); succeeding character positions need not be used.

/0 - Link display

One-character alphabetic code that controls the suppression of a link display from a 700-785 field.

a - Link not displayed

Used for a local system-dependent reason for suppression that is not covered by code b or c. For interchange purposes, code a is converted to code n or a fill character (|).

008/09 a
[established heading record]
008/11 a
[code indicating LCSH]
110 2#$aLast Poets (Group)
710 27$wa$aLast Poets$2 [source code]
[Record for the linking entry form of the name is not in LC system.]
b - Link not displayed, field 788 used

Generation of a link display from a 700-785 field is suppressed because of the existence of field 788 (Complex Linking Entry Data) in the record.

008/09 a
[established heading record]
008/11 c
[code indicating MeSH]
150 ##$aReferral and Consultation
750 #0$81$wb$aMedical referral
750 #0$81$wb$aMedical consultation
[The two LCSH headings are the equivalent of the MeSH heading.]
c - Link not displayed, non-7XX field used

Generation of a link display from a 700-785 field is suppressed because a non-7XX field (e.g., 360, 680) in the record describes the relationship.

008/09 a
[established heading record]
008/11 a
[code indicating LCSH]
150 ##$aCorrosion and anti-corrosives
360 ##$isubdivision$aCorrosion$iunder individual materials, metals and metal compounds and types of engineering structures, equipment, and vehicles. e.g.$aConcrete-Corrosion; Copper-Corrosion; Automobile -Corrosion
780 #0$wc$xCorrosion
n - Not applicable

Used when there is no restriction on displaying a link from the 7XX field. If code n is applicable, subfield $w/0 need not be used.

/1 - Replacement complexity

One-character alphabetic code that indicates the possibility of automatic replacement of a heading in a 700-785 field.

a - Heading replacement does not require review

Headings that are always used to replace the obsolete heading (i.e., headings that can be machine substituted without requiring manual review).

040 ##$aDLC$dOCLC$ffast
150 ##$aSummer resorts
550 ##$aResorts
550 ##$aSeaside resorts
750 #0$aSummer resorts$0(DLC)sh#85130430#$wna
b - Heading replacement requires review

Heading may be used as a replacement, but requires subject analysis to determine its appropriateness (i.e., headings that should be used as replacements only after manual review).

040 ##$aDLC$dOCLC$ffast
151 ##$aMichigan$zCharlevoix
751 #0$aCharlevoix (Mich.)$0(DLC)n##82062705#$wnb
n - Not applicable

Heading is not being replaced by another heading. If code n is applicable, $w/1 need not be used.

$2 - Source of heading or term

MARC code that identifies the thesaurus or authority file that is the source of the heading when the second indicator position contains value 7. Code from: Subject Heading and Term Source Codes for subfield $2 in fields 700-751, 780-782, and 788; and Genre/Form Code and Term Source Codes for subfield $2 in fields 755 and 785; and Musical Instrumentation and Voice Code Source Codes for subfield $2 in field 762.

008/09 d
[subdivision record]
008/11 r
[code indicating AAT]
185 ##$vatlases
755 #7$vatlases$0 [record control number] $2aat
008/09 a
[established heading record]
008/11 r
[code indicating AAT]
155 ##$aatlases
785 #7$vatlases$0 [record control number] $2aat
[The same heading is used both as a subject and as a subdivision term in the Art & Architecture Thesaurus]

$4 - Relationship code

Contains in coded form the designation of a relationship of the entity in a 7XX field to the 1XX entity in the record. Code from: ISO 25964-2: Thesauri and interoperability with other vocabularies — Part 2: Interoperability with other vocabularies, Section 4, Table 1.


INPUT CONVENTIONS

General Input Conventions - General input conventions for the 7XX fields are provided in the General Information sections for each type of heading (X00 Personal Names; X10 Corporate Names; X11 Meeting Names; X30 Uniform Titles; X48 Chronological Terms, X50 Topical Terms; X51 Geographic Names; X55 Genre/Form Terms; X62 Medium of Performance Terms; X80 General Subdivisions; X81 Geographic Subdivisions; X82 Chronological Subdivisions, X85 Form Subdivisions).

Order of Subfields - Subfields $6 and $5, when they are used, are the first and last subfields, respectively, in a field. When these and other control and linking subfields are used in a 7XX linking entry field, they occur in the following order.

$6 $8 $w <heading subfields: $a, etc.> $0 $2 $5

Relationship Codes - Generally used appropriate relationship codes are from ISO 25964-2: EQ (Equivalence), BM (Broader mapping), NM (Narrower mapping), RM (Related mapping). Also, according to ISO 25964-2, refinements can be expressed by additional symbols.

Display Constants for Linking Entries - In the 7XX linking entry fields, phrases such as those listed below are not carried in the MARC record. They may be system generated as display constants associated with the field tag.

When the 1XX and 7XX headings are from different systems or thesauri, a display constant may be a combination of a tag-related phrase like one of the above and either coded or textual data generated by the value in the second indicator position (Subject heading system/thesaurus) or the source code in subfield $2 (Source of heading or term).

For field 788, the complete display constant may be a combination of a tag-related phrase and explicit text contained in subfield $i (Explanatory text).


CONTENT DESIGNATOR HISTORY

Field 748 - Established Heading Linking Entry - Chronological Term [NEW, 2002]
Field 762 - Established Heading Linking Entry - Medium of Performance Term [NEW, 2013]
Field 9XX - Equivalent Headings [OBSOLETE, 1997] [CAN/MARC only]
$i - Relationship information [NEW, 2014]
$v - Form subdivision [REDEFINED, 1995] [USMARC only]
$u - Record control number [OBSOLETE, 1997] [USMARC only]
$0 - Record control number [NEW, 1997]
$4 - Relationship code [NEW, 2014]
$w/1 - Replacement complexity [NEW, 2002]

Library of Congress >> MARC >> Authority >> 7XX
(10/20/2014)
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